Strategy for getting my 40mm EP, exit pupil and scope to do fields etc.

[Nightspore]

45 minutes ago, Tufty said:

Yup this is why I signed up here, to find out how more experienced people do it and pick their brains!  Many thanks.  I guess the CA seems to me to be so well controlled in the f9.4 achro on moon Jupiter and Saturn, and other objects,  that I was having high expectations of Mars - but haven't had the opportunity to put the two together yet.  I take what you say as I have used the Equinox on Mars a few times. I do experience some bizarre CA on Mars (even at x50) with it but not on other things.  The Altair Starwave, I just looked, is a triplet apo and advertises as CA-free.... I can see myself starting a telescope arsenal!

 

Hmmm, I've got Mars on my list as something I want to keep coming back to.  Given what you say I will probably have to rethink my scope 'strategy' again. Something to show some Martian detail will be one of my essential (as opposed to merely desirable) tick boxes.  Still, I'll be keeping the 5" achro as nothing else I've ever wanted that I've finally got has delivered as well as this (except maybe a film camera I bought some time ago).

 

Thanks for the BAA link, very interesting and I'll be on it like a car bonnet now I've had a 'clear' night spoiled by dew!  I was thinking of joining the BAA at some point funnily enough.

 

My Starwave is a doublet.

 

 

You're getting CA with the Equinox? Are you sure it's CA? You should see Martian detail with the Equinox, although you'll need around 200x. There's nothing wrong with your 5" achro, it's just not a planetary scope. Deep sky and rich field should be fine though.

[Tufty]

 

14 hours ago, Nightspore said:

ou're getting CA with the Equinox? Are you sure it's CA? You should see Martian detail with the Equinox, although you'll need around 200x. There's nothing wrong with your 5" achro, it's just not a planetary scope. Deep sky and rich field should be fine though.

 

Not sure if CA in the equinox, not in the same sense as in the achro.  I can't get up to x200 with it yet as I don't have the kit for that. I can do x125 but mars is exceptionally bright in it, so if there is detail I can't see it for that reason at least.

 

But the good news is that Mars, my achro and I were all together at the same time last night and I got nearly 2 hrs. The view at x120 was very good. For the first time I saw a little row of darker patches on the orange disc. No polar caps though.  I tried it with a x2.5 Barlow as well but somehow a halo of mist kept appearing after a few minutes and I had to stand back and wait for it to clear. Maybe I need to wear a mask.  Again I didn't see much CA with the Barlow, but I did most of the viewing at x120 which gave me the sharper detail.  So I was very happy! 

 

The advertising for these achros is mainly as moon and planets scopes. The focal length makes things darker than in the equinox and the fov is smaller, so I'm surprised if you see them as goid for dso. I have seen the orion nebula with it which is great. I have great problems getting up on cygnus and cassiopeia as the eyepiece is around my knees! The retailer sent me a column extension but it didn't fit my mount.  I had been thinking of getting a newtonian mak for dsos or using the equinox with 2" eps as per previous conversations in this thread.  But I'm getting confused lol 😆 

[Nightspore]

2 hours ago, Tufty said:

 

 

Not sure if CA in the equinox, not in the same sense as in the achro.  I can't get up to x200 with it yet as I don't have the kit for that. I can do x125 but mars is exceptionally bright in it, so if there is detail I can't see it for that reason at least.

 

But the good news is that Mars, my achro and I were all together at the same time last night and I got nearly 2 hrs. The view at x120 was very good. For the first time I saw a little row of darker patches on the orange disc. No polar caps though.  I tried it with a x2.5 Barlow as well but somehow a halo of mist kept appearing after a few minutes and I had to stand back and wait for it to clear. Maybe I need to wear a mask.  Again I didn't see much CA with the Barlow, but I did most of the viewing at x120 which gave me the sharper detail.  So I was very happy! 

 

The advertising for these achros is mainly as moon and planets scopes. The focal length makes things darker than in the equinox and the fov is smaller, so I'm surprised if you see them as goid for dso. I have seen the orion nebula with it which is great. I have great problems getting up on cygnus and cassiopeia as the eyepiece is around my knees! The retailer sent me a column extension but it didn't fit my mount.  I had been thinking of getting a newtonian mak for dsos or using the equinox with 2" eps as per previous conversations in this thread.  But I'm getting confused lol 😆 

 

You won't really see much detail until you can get about 200x. At 120x brightness on Mars is going to be a problem. Polarising filters can help. Light blue filters can help with the caps if they're difficult. The Northern Polar Hood clouds are still pretty visible apparently. The NPH are often mistaken for the north pole by many inexperienced observers. Polarising filters are also useful for a bright Venus. Sometimes cloud detail can be seen on Venus. Best to view it in twilight. 

 

 

Admittedly I tend to use faster achro's for deep sky. What manufacturer's claim and what's actual reality don't always agree. Most entry level achro's are sold as something they're not and are often bundled with hopelessly underweight mounts. I don't know much about Mak-Newt's but I've never seen the advantage of a Newtonian that dews. 

 

 

Bear in mind a 150mm conventional Newtonian will have at least a 40 min cool down, usually longer. Check the warm air vortices by using a defocused eyepiece. The first time I witnessed this phenomena I was quite shocked. An OTA enclosed with a meniscus lens will take even more time. There's a reason large Newtonians have cooling fans!

Edited November 23, 2022 by Nightspore

[Tufty]

Wow OK. I was advised away from fast achros ie short ones because of CA. So I got a long one! Breeze now and we've had rain today but forecast said clear  but Jupiter isn't as good as I've seen it with the same scope. Can't go over x120 this eve. It's on an eq5 BTW. 

 

I do tend to set up the scopes then go away for an hour or so. But it would be good to have that 'ready immediately' scope. I thought the equinox would be that.  Yes a mak I've heard needs a while to sort itself out, so that's an issue.  A newtonian hmm for some reason not overly excited although when I move I want to get a dob!! 

 

I think I have a polarising filter which the man in the shop said I'd like for the moon.  I'll try it on Mars. But I can see from what you say Mars is a bit technical. My learning curve is shifting! 

[Nightspore]

TBH you're going to need a better filter for Mars eventually. I'd recommend the Baader Contrast Booster. Although a yellow filter would help. Baader Neodymium at least. Some of the magenta 'Mars filters' can work well for darker albedo features.

[Tufty]

19 hours ago, Nightspore said:

TBH you're going to need a better filter for Mars eventually. I'd recommend the Baader Contrast Booster. Although a yellow filter would help. Baader Neodymium at least. Some of the magenta 'Mars filters' can work well for darker albedo features.

Yes, a contrast booster has come up a couple of times. Sounds like the thing.  I havent had any luck with the IR cut neodymium in either scope, but I read somewhere, for achros, contrast filters are the thing.  I think of yellow as increasing contrast in photography so that sounds very sensible.  Worth it to see more of Mars!

[Nightspore]

51 minutes ago, Tufty said:

Yes, a contrast booster has come up a couple of times. Sounds like the thing.  I havent had any luck with the IR cut neodymium in either scope, but I read somewhere, for achros, contrast filters are the thing.  I think of yellow as increasing contrast in photography so that sounds very sensible.  Worth it to see more of Mars!

 

I'm not sure what the CB was originally intended for, but it can be used with any kind of scope. It isn't just a 'yellow' filter and the substrate/curve is quite complex. It's generally considered to be the finest overall Mars filter. Which I'd agree with.

 

[Nightspore]

This Tele Vue Bandmate is the best magenta Mars filter I've ever used.

 

 

It is now discontinued. The Celestron is pretty good, although I can't vouch for its availability.

 

 

Above: screenshot from SkySafari. For a couple of nights last opposition the seeing was really good. I could recognise this area (Valles Marineris), particularly the darker albedo 'delta' area with the Starwave (240x). Obviously not as big, and I couldn't properly see the Valles itself of course, but I could make out the dark delta just underneath it. I could just make it out with the 80ED at 240x as well. I doubt it could have been achieved without FPL-53 glass. There'd be no chance with an achromat.

 

Maybe something like this old Polarex f/15 achromat. Although it's only 60mm. I never owned anything like this but they were popular until affordable Chinese ED glass scopes were more easily available.

Edited November 25, 2022 by Nightspore

[Tufty]

I read somewhere, but can't now find it, that some contrast filters suit only apos and don't do any good in achros. But something I need to delve into clearly. I'd like to see if I could get a tad more contrast in the achro at the same time as dimming the brightness on Jupiter.

 

Mars: What do you do to your ed 80 to get x240 ?  I see it has only a slightly longer FL than the equinox. Are you using a x2 Barlow and a 5mm ep? Is that stable, easy tracking? What is your main use of the 80? I see it is sold with 2" diagonal and 2" 28mm ep - which is the direction I think I'm now going in with the Equinox- so many questions lol! 

 

CA report: I had time yesterday eve  to poke the equinox bit further. Saturn is low, we had rain 2hrs before I started viewing. I don't get much if any CA in the achro using the ES eps. In the equinox it is variable particularly at the edges, after some time it worsens, I don't know if all the mist I produce is somehow not clearing from the optics? I put in an Orion zoom ep 24-8mm. It's not something I use much as I don't think much of it. However, focusing at 8mm gave a great, very tight CA-free view of Saturn.  The ep is very tall with long rubber so the eye is a good distance from the glass and well insulated from the nose! 

 

On Jupiter the ES was better but contrast was not so good last night.  The ES do work really well with the achro but I'm questioning them with the Equinox. I'm thinking of changing ep brand as I branch out into 2" for the wide field 

 

Your comments are appreciated! 

[Nightspore]

53 minutes ago, Tufty said:

I read somewhere, but can't now find it, that some contrast filters suit only apos and don't do any good in achros. But something I need to delve into clearly. I'd like to see if I could get a tad more contrast in the achro at the same time as dimming the brightness on Jupiter.

 

Mars: What do you do to your ed 80 to get x240 ?  I see it has only a slightly longer FL than the equinox. Are you using a x2 Barlow and a 5mm ep? Is that stable, easy tracking? What is your main use of the 80? I see it is sold with 2" diagonal and 2" 28mm ep - which is the direction I think I'm now going in with the Equinox- so many questions lol! 

 

CA report: I had time yesterday eve  to poke the equinox bit further. Saturn is low, we had rain 2hrs before I started viewing. I don't get much if any CA in the achro using the ES eps. In the equinox it is variable particularly at the edges, after some time it worsens, I don't know if all the mist I produce is somehow not clearing from the optics? I put in an Orion zoom ep 24-8mm. It's not something I use much as I don't think much of it. However, focusing at 8mm gave a great, very tight CA-free view of Saturn.  The ep is very tall with long rubber so the eye is a good distance from the glass and well insulated from the nose! 

 

On Jupiter the ES was better but contrast was not so good last night.  The ES do work really well with the achro but I'm questioning them with the Equinox. I'm thinking of changing ep brand as I branch out into 2" for the wide field 

 

Your comments are appreciated! 

 

A filter is a filter, whether it's specifically a 'contrast' filter is debatable. Although yellow filters are often used, so are other colours depending on what you are observing and wanting to contrast. The terms 'achromat' and 'apochromat' both mean without colour and were originally just marketing terms. Dollund's telescopes were first described as 'achromatic' as they were at that time the best corrected refractors in the world. 'Apochromat' and 'semi apochromat' are from the German and originally used by Zeiss in marketing ED glass scopes I believe. The difference between an achromat and apochromat is just between better degrees of colour correction.

 

Jupiter is a bit bright at the moment anyway, just increasing the magnification would improve it. Although most modern achromatic scopes aren't good above 100x unless they're very slow (f/15-25).

 

I have a 2.5mm TS HR. At f/7.5 I see the 80ED more as a planetary scope but it can do rich field at a pinch and a general all-rounder. It's just slow enough to use a reversed Kellner occasionally. It's bundled with a 2" eyepiece, although it's also bundled with two 1.25" in the US. It's just marketing. Tracking with an alt-az at high magnifications takes practice lol.

 

 

[Tufty]

A 2.5mm ep!! I didn't know they existed! Just had a look, the ts seems to be cheap enough for a punt.  If it worked for me it would turn my 80 into a bit more of an all-round  travel scope as well. 

 

I heard Brian Cox say something along the lines that apos are overhyped.  It seemed to me that the better correction, glass etc seems to be put with much shorter FLs so there must be a cross over point where an apo and achro have similar performance levels on ça, other things aside like AP exposure times etc.  So I wouldn't be surprised if your Polarex didn't have good moments.  I have been giving the 102 Srarwave some thought in the last few days as well! But as you say I'm probably at the stage where I need to play around with eps a bit more.

 

Thanks for the thoughts! 

[Nightspore]

 

These were my main 'Mars' eyepieces/filters last opposition with the 80mm Evostar.

 

The difference between the different sort of ED glass comes down to what you pay for them. Shorter f/l are aimed at the AP market. An f/15-25 achromat could hold its own along shorter f/l ED scopes, but they are long and difficult to use. 

 

 

The ST102 at f/4.9 is the best rich field scope I have. It's pointless for lunar/planetary though.

Edited November 26, 2022 by Nightspore

[Nightspore]

Oh yeah, I never actually owned a Polarex. I did have a Tasco though.

[Tufty]

Amen to the idea f/15 achros might be difficult to use! I can say with the little experience I have that my f/9.4  4'6" scope can be awkward! 

 

Putting data in a fov calculator for my 80ed and the TV 3mm you show I get <0.5mm exit pupil. So I think I'd have to try that out to see if it worked for me.  So I have a lot of trying out to do! I'll just play around with the 80 and see what it can do, it's not going to work for planetary I feel, so maybe I'll look gor a dedicated reducer or something if it doesn't natively like the widefield, but right now I'm hoping it will! 

[Moonlit]

On 11/23/2022 at 3:26 PM, Nightspore said:

Bear in mind a 150mm conventional Newtonian will have at least a 40 min cool down, usually longer. Check the warm air vortices by using a defocused eyepiece. The first time I witnessed this phenomena I was quite shocked. An OTA enclosed with a meniscus lens will take even more time. There's a reason large Newtonians have cooling fans!

Interesting point about seeing turbulence by defocusing the image, .
I've planned on lining the inside of my soon-to-be-delivered Newt with cork painted black to prevent cooling the air blowing from the fan, and making sure the fan actually blows air past the sides of the mirror so it takes the hot air on the surface of the mirror with it. Got lots of articles about shaping a baffle that causes the air to go the right way, so I achieve laminar flow upwards. Can't wait to get started on that!

[Moonlit]

An update on preventing dew: I purchased a bit of Low-E insulation, which is 6.5mm thick made of bubblewrap (actually much smaller air bubbles) sandwiched between two sheets of tough aluminium foil.
It is marketed as a low emissivity insulation that prevents objects from losing heat through infrared radiation.

I had set up an experiment where I placed three soda cans on a wooden rack on the lawn outside, them being full of carbonated water at room temperature when I placed them.
One was just a normal can, one was wrapped in a thick velvety cloth like the picture I posted earlier, and the last wrapped in Low-E.

I took this picture with my FLIR One camera after leaving them out for 30 minutes. 
Left: uncovered can
Middle: cloth covered can
Right: Low-E covered can

As you can see the Low-E loses almost no heat through IR radiation, while the cloth actually seems to make things worse!

Annoyingly, when I went out after 60 minutes to do another reading som neerdogoods had kick my rack over and stolen the cans! Thieves! So I didn't get to unwrap them after a few hours and actually measure how cold they each had become, but I don't think the experiment is even necessary.

So I will be covering my telescope (and my diagonals and EPs!) in Low-E. It cost me around £12 for 1 square meter plus some insulating tape to keep it in place. I'm sure plenty of other brands of low emissivity insulation are available.

Edited November 28, 2022 by Moonlit

[Nightspore]

1 hour ago, Moonlit said:

Interesting point about seeing turbulence by defocusing the image, .
I've planned on lining the inside of my soon-to-be-delivered Newt with cork painted black to prevent cooling the air blowing from the fan, and making sure the fan actually blows air past the sides of the mirror so it takes the hot air on the surface of the mirror with it. Got lots of articles about shaping a baffle that causes the air to go the right way, so I achieve laminar flow upwards. Can't wait to get started on that!

 

Yeah, it's scary lol. I couldn't believe how much turbulence there was in a 6" Newt.

[Nightspore]

3 hours ago, Tufty said:

Amen to the idea f/15 achros might be difficult to use! I can say with the little experience I have that my f/9.4  4'6" scope can be awkward! 

 

Putting data in a fov calculator for my 80ed and the TV 3mm you show I get <0.5mm exit pupil. So I think I'd have to try that out to see if it worked for me.  So I have a lot of trying out to do! I'll just play around with the 80 and see what it can do, it's not going to work for planetary I feel, so maybe I'll look gor a dedicated reducer or something if it doesn't natively like the widefield, but right now I'm hoping it will! 

 

There's no reason the 80 shouldn't work for planets. One of the best images I ever got with Saturn was at oppo' with the 80ED DS Pro at 200x. An 80mm quality refractor can rival a 5" reflector.

[Tufty]

@MoonlitI'm amazed at your appetite for empirical science!  I am thinking of dew now more than at any other time in my life!  Your Low-E looks like one version of central heating radiator insulation.  I am very interested in this if it works.  I've read about others using this, or similar, stuff to wrap their scopes in.  Maybe a photo with yours wrapped!?  I'm thinking of a 'coat' with a zip fastener to go from focuser to the end of the dew cap.  I wonder if a heat band would also be necessary? Good use of a thermal imaging camera - sorry you lost your tins.

 

On 11/28/2022 at 9:50 PM, Nightspore said:

 

There's no reason the 80 shouldn't work for planets. One of the best images I ever got with Saturn was at oppo' with the 80ED DS Pro at 200x. An 80mm quality refractor can rival a 5" reflector.

 I don't doubt it!  I don't think I'm ready for newtonians yet anyway, if I ever do get one I'd want it big and somewhere it could stay set up.  You said images of Saturn which I suppose is a slightly different situation. I've seen nice oics of planets taken on very small refractors with all the software wizardry etc. AT the moment my FL@500 is on a camera mount, I can't use it visually with high magnification.  I need to get a dovetail for it and put it on a proper mount and improve my EP collection of 4 x eps!! Since we've been talking you've got me looking a lot at the Altair and ES triplets c f/7 102, 127, 130 - I nearly jumped during the black friday discount this week but nagged myself I need to think through the ep situation more first...but then agan...!

[Nightspore]

Triplets can work but they're only as good as a high quality doublet (FPL-53) for strictly visual. Not only are they more expensive, they are heavier and have a longer cool down. A very good doublet can have better visual acuity than a triplet. I tend to stick to doublets for visual only. My 102mm Starwave is 4 kilo, and that's without diagonal, eyepiece and finder. 2" accessories can add a kilogram.

 

 

A 102mm triplet would be heavier.

Edited December 1, 2022 by Nightspore

[Tufty]

Good points. The marketing on the carbon fibre triplets is enticing ie portable, good for visual and AP, planets and dsos supposedly etc etc. The all in one solution! But as you say the 2" accessories add weight too. I think my long term plan of just finding the right wide field eps to work with the Equinox(Im thinking of the panoptics you suggested) is currently getting distracted by Mars coming into opposition and being high and bright and not having the kit to make the most of it today!