I'd like to hear some thought on F7 Refractors

[paulgrover68]

I currently have 2 scopes - my 72EDF and a 200PDS.

I've been using the 72 over the winter and it has been a real pleasure - I love that little scope! I use it with 0.8 reducer so it's wide 345mm focal length.

With spring coming, I plan to go back onto my newt. Once it's up and running it's great, but it has some girth. And then there is  collimation.

Now I used to think Collimation wasn't a big deal until I didn't have to do it, now I think it the most urrrggghhh thing in the universe (first world problems!)

 

The Altair Wave Series 115 Triplet APO has caught my eye (there are some good words in its name - like triplet and APO).

With an FL of 850 it would be the perfect size to replace the reduced 200P-DS. However it's F7 out of the box.

The implication of that is exposure times will increase (it currently use 3-5 mins on the targets I picked last year)

So I guess the main question is how is it shooting at F7? Would I need to change too much coming from the Newt?

(My ultimate aim is to have 2 rigs - a big one for small stuff and a small one for big stuff)

Thanks in advance

 

[AstronomyUkraine]

19 hours ago, paulgrover68 said:

I currently have 2 scopes - my 72EDF and a 200PDS.

I've been using the 72 over the winter and it has been a real pleasure - I love that little scope! I use it with 0.8 reducer so it's wide 345mm focal length.

With spring coming, I plan to go back onto my newt. Once it's up and running it's great, but it has some girth. And then there is  collimation.

Now I used to think Collimation wasn't a big deal until I didn't have to do it, now I think it the most urrrggghhh thing in the universe (first world problems!)

 

The Altair Wave Series 115 Triplet APO has caught my eye (there are some good words in its name - like triplet and APO).

With an FL of 850 it would be the perfect size to replace the reduced 200P-DS. However it's F7 out of the box.

The implication of that is exposure times will increase (it currently use 3-5 mins on the targets I picked last year)

So I guess the main question is how is it shooting at F7? Would I need to change too much coming from the Newt?

(My ultimate aim is to have 2 rigs - a big one for small stuff and a small one for big stuff)

Thanks in advance

 

 I have just recently bought an Esprit 120, it has a FL of 840 and is f7. I still use the same exposure times I used with my 80ED. With a reducer my 80 ED is reduced to an f5.1, more or less the same as your Newt, and I changed little, same gain and exposure times. The only difference from my previous setup is instead of a reducer/flattener, I use a flattener, and keep the f7 for galaxy season. Once the nebula come around again, I will buy a 0.77 reducer for NB work. My advice if you do purchase the apo, just try various gain and exposure lengths, and see what works for you.

 

Brian

[paulgrover68]

Awesome - thanks Brian. That pretty much echoes my thoughts.  My idea is to keep the .8 reducer on my 72 to go wide, then initially keep he 115 unreduced for small DSO and galaxies. 

The next thought in that progression is to consider .8 on the 115 at a later date to get an intermediate focal length of around 690. That would cover a lot of bases.

 

[MartinS]

Hi Paul, I have the usual set of triplets, mostly at F7, AA130 EDT, TS130, AA 102 EDT, 81,80 and 60mm. I find their contrast and low maintenance is greatly satisfying and with the readily available reducers you can cover all bases in between. 

My two 130 triplets were set up in a dual imaging rig and were great when using the 383 cameras, enabling me to get sufficient images with long exposures. Since these were replaced with the 455/571 faster sensor cameras I found the need for a dual rig (2 instances of SGP etc) setup diminished beyond the pitfalls so now I run a 130, 81 and 60mm setup on one system to give me greater target flexibility.

If you are after a good flexible setup, I would recommend you also consider 130 triplets as they offer a great range with the available reducers from 910mm through 719, 570 with the readily available reducers.

Good luck with your endeavour.

 

Martin

[MarkAR]

I have the Altair Wave 115EDT and I can't fault it at all. I use the Planostar 0.79 FF/reducer at the moment and have been taking 2 to 20 minute exposures depending on target. Been waiting nearly a year for the 1.0x Planostar to come back into stock to go for slightly smaller targets.

Edited March 17, 2021 by MarkAR

[paulgrover68]

Thank you all - massively useful and... next week there will be a new kid in town. 

I think the only person who'll miss the laser collimater is the dog. That little red dot is his nemesis.