Jump to content
Welcome to Backyard Astronomy Space - please register to gain access to all of our features. Click here for more details. ×

Pearls of wisdom - The advice you wish you'd followed


EwanV

Recommended Posts

We all know what it's like - a friend passes on a great piece of advice and you ignore it, only to regret it almost immediately.  This thread is for those of us who "thought they new better" and want to save others from the same mistake as well as the smug gits who's mate saved them a fortune.

 

Let's start with this one from a very good friend of mine about cleaning your mirrors and lenses:

 

"If you ever get the urge to clean your primary mirror or objective lens, the first step is to make a cup of tea and sit down until the feeling has passed"

 

So you've got a dusty primary mirror.  It's a 150mm diameter, so it's surface area is (75mm x 75mm x 3.14) 17,662.5mm^2.  That's a lot of square millimeters!!  A dust particle will be 1 to 100 microns in diameter (0.01 to 0.1mm) and if you do the maths you'll see that you would need somewere between 2,250,000 and 225,000,000 dust particles to completely cover your mirror.  The dust stands out when you look at the mirror, but you don't notice all the gaps between the particles.  Let's say that you've been unlucky enough to get 100,000 particles of an average 50 microns across.  That's (0.025mm x 0.025mm x 3.14 x 100,000) 196.25mm^2 or just over 1% of your mirror. 99% of it is still clear.  The clips holding the mirror in place are actually covering more surface area than the dust!!!!  LEAVE IT ALONE!!!!

 

 

 

  • Like 1
Link to comment
Share on other sites

I don’t have any pearls of wisdom (relating to astronomy anyway) as I only have a few months experience. However, I read the above with great interest, it’s put very well. It’s one I will remember.

 

A very quick non Astro pearl would be ‘Dont eat yellow snow!’

Link to comment
Share on other sites

AstronomyUkraine
2 hours ago, EwanV said:

We all know what it's like - a friend passes on a great piece of advice and you ignore it, only to regret it almost immediately.  This thread is for those of us who "thought they new better" and want to save others from the same mistake as well as the smug gits who's mate saved them a fortune.

 

Let's start with this one from a very good friend of mine about cleaning your mirrors and lenses:

 

"If you ever get the urge to clean your primary mirror or objective lens, the first step is to make a cup of tea and sit down until the feeling has passed"

 

So you've got a dusty primary mirror.  It's a 150mm diameter, so it's surface area is (75mm x 75mm x 3.14) 17,662.5mm^2.  That's a lot of square millimeters!!  A dust particle will be 1 to 100 microns in diameter (0.01 to 0.1mm) and if you do the maths you'll see that you would need somewere between 2,250,000 and 225,000,000 dust particles to completely cover your mirror.  The dust stands out when you look at the mirror, but you don't notice all the gaps between the particles.  Let's say that you've been unlucky enough to get 100,000 particles of an average 50 microns across.  That's (0.025mm x 0.025mm x 3.14 x 100,000) 196.25mm^2 or just over 1% of your mirror. 99% of it is still clear.  The clips holding the mirror in place are actually covering more surface area than the dust!!!!  LEAVE IT ALONE!!!!

 

 

 

The old saying comes to mind with astrophotography, "if it ain't broke, don't fix it". I have been guilty of this myself many times. Trying to get the guiding a little more precise, and making it worse, is my failing.

Link to comment
Share on other sites

"Buy the biggest, heaviest mount you can reasonably afford and carry".

 

This was the second piece of advice I followed, but only after making two dreadful mistakes!  Now I'm talking about deep sky astrophotography here.  There's an amazing amount of stuff you can achieve with a standard DSLR and tripod, a muddy field and a load of spare batteries, but if you want to create a decent long exposure deep sky image you need something that's going to act like a rock rather than a sail when the wind blows.  Additionally, you want something that is going to last and be useful for a wide range of scopes - there's no point trying to mount an 8" Newtonian on an EQ3.

 

My view is that your main telescope shouldn't weigh more than 50% of the carrying capacity of your mount.  Your mount has to carry your guide scope, guide camera, main camera, dew straps, focusers, bits, bobs and doodas so keeping your main scope to 50% of the capacity or below means you're mount isn't overworked.  Additionally, there isn't one scope that will do EVERYTHING so even if you start with just one telescope you're likely to end up with several. 

 

On the back of the above advice, I bought a second hand HEQ5.  I've used everything from an 8" Newt to (my current) 72mm refractor over the last 6 years.  I've owned more scopes than I can count, but the mount is still going strong.

 

 

Link to comment
Share on other sites

Nightspore
4 minutes ago, EwanV said:

Additionally, there isn't one scope that will do EVERYTHING so even if you start with just one telescope you're likely to end up with several. 

 

 

 

 

 

This does everything:

 

o2uFxM5l.jpg

 

And I have several scopes lol.

Link to comment
Share on other sites

15 hours ago, Nightspore said:

 

This does everything:

 

o2uFxM5l.jpg

 

And I have several scopes lol.

I love my 72mm frac but if you want to get close and personal with things like the Virgo Cluser of Galaxies you need something with a wide aperture and long focal length.  The 72 does lovely wide shots of the VCoG but my best shot of the Blowdryer Galaxy (M100?) was with a Ritchey Cretien

Link to comment
Share on other sites

Having seen that this thread was started in ‘getting started equipment advice’ I thought it may be appropriate to give what advice I can to anyone else reading this who is just starting out, as I was a few months ago.

 

I would simply say don’t jump in with both feet and commit yourself to a large financial outlay until you know what you want/expect from the hobby.

 

There are many sides to this hobby and different scopes excel in different areas. (Observing, Astro photography, planets, DSOs etc).

So take your time and resist the temptation to buy those expensive shiny new toys until you know what is right for you.

There is a thriving used market with possible respectable savings. This is potentially a way into the hobby allowing unsuitable equipment to be ‘moved on’ and changed, upgraded without any large losses.

There is much on the used market being sold by people who have made just this mistake. Ie selling up due to wanting to change scopes after a relatively short time.

 

Good luck to anyone entering into this fascinating pastime. There is a lot to consider and learn. Spend your money wisely and the rewards will amaze you.

 

 

Link to comment
Share on other sites

Nightspore
1 hour ago, EwanV said:

I love my 72mm frac but if you want to get close and personal with things like the Virgo Cluser of Galaxies you need something with a wide aperture and long focal length.  The 72 does lovely wide shots of the VCoG but my best shot of the Blowdryer Galaxy (M100?) was with a Ritchey Cretien

 

Well, it does nearly everything lol. If I had to think of a 'pearl of wisdom' to give to someone interested in visual observing it would be to recommend a decent ED doublet around f/7 and at least 4" of aperture. 

 

9ICu4rul.jpg

 

A 102mm, f/7 ED refractor can do just about everything and isn't too large to be difficult to set-up fairly easily. I started out with a 50mm Tasco refractor when I was still at school. I have a few reflectors of various types. I'm physically disabled now which seriously dictates the aperture size I can comfortably use. 

 

kz9EL60l.jpg

 

My only other 'pearl' would be to say that I believe people should enjoy their observing and not obsess too much about equipment. Some of the most enjoyable nights I've ever had have been with an inexpensive 80mm short tube achromat.

 

 

Link to comment
Share on other sites

paulgrover68

I have nothing specific. I would say starting imaging with a small refractor is good advice I considered but ultimately went with a newt. At the time I was starting to get into imaging, but had no idea if I would be sucessful - newt + coma corrector was £100 less than refractor + reducer. So it made sense

Later I bought a 72EDF and it unlocked a lot of options - and reduction in setup time.  Did this superseed the newt? Not initially as I used both. I did subsequently replace the newt with a big triplet (sold the newt for what I paid for it - the upside of the pandemic stock shortage and supplier price increases)

Link to comment
Share on other sites

I cleaned the mirror of my old 6" reflector today.  I put in under the tap in the sink, and gently (and I mean gently) rubbed the surface using my fingers and soap, thoroughly rinsing, followed by a final rinse using distilled water.  I've done this many times on many mirrors. Modern mirrors have a tough silicon dioxide coating that isn't damaged by this process.

 

In my opinion, the problem isn't the small area obscured by the dust, its the scattered light it produces, which reduces image contrast.  Professional observatories clean their mirrors regularly, often using carbon dioxide gas jets to blow off the dust, so I guess they must think this necessary.

Link to comment
Share on other sites

Nightspore
24 minutes ago, mechanoid said:

I cleaned the mirror of my old 6" reflector today.  I put in under the tap in the sink, and gently (and I mean gently) rubbed the surface using my fingers and soap, thoroughly rinsing, followed by a final rinse using distilled water.  I've done this many times on many mirrors. Modern mirrors have a tough silicon dioxide coating that isn't damaged by this process.

 

In my opinion, the problem isn't the small area obscured by the dust, its the scattered light it produces, which reduces image contrast.  Professional observatories clean their mirrors regularly, often using carbon dioxide gas jets to blow off the dust, so I guess they must think this necessary.

 

I've often wondered about this. I rarely clean the primary on my 150mm GSO Newtonian.

 

CqTx1vG.jpg

 

But I know a few people who do regularly clean their mirrors in a very similar fashion to the way you described. I have a feeling it doesn't do them any real harm. Although I wouldn't recommend overcleaning a refractor objective.

Link to comment
Share on other sites

My first real scope was the 250mm. Back in 2005 I bought it as excess stock from Greenwich, bundled with an EQ5 mount with no motors. A combination completely not appropriate for imaging and only just good enough for visual. But I had fun observing and trying to do stuff more advanced hobbyists would not bother with even then. As a result I have pictures I am very happy to have in my collection. Poor quality pictures yes but achievements and memories. 

 

I need to take my own advice and remember to have fun with astronomy!

 

First light with that scope and a cloud came over and dumped acid rain from the cement works all over the primary. That etched the glass with big very visible splotches😭. I washed the mirror twice in that time. I used the scope like that on and off until last year when I had it re-silvered. I always thought the blemishes might have an effect but the conditions never allowed it to reach full potential and I wasn't imaging for more than an hour per target so light pollution and camera noise were always dominant. 

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...