thoughts on spotting scope vs astronomy scope

[jeelan (Jeelan)]

hey all,

just wanted some thoughts on spotting scope vs small 80mm astro refractor.

For context - we currently take a spotting a scope and binos with us whenever we go camping. Its great because we can use the scope for wildlife viewing, birds, and around the beach use it for whale watching as well..

Since getting back into Astronomy, I've been tempted to get something that we can use for stargazing.

So i've been thinking about getting a small (80mm) refractor but wanted something that could potentially replace the spotting scope as well. I'm not fussed about portability (to a certain extent) as camping is done by car/camper trailer so scope would sit in the back of the car.


Currently i'm looking in the $1500-$2000 mark so Skywatcher Esprit 80ED, Orion ED80T, and Williams Optics GT-81 are the front runners..

Just wondering what people's thoughts are on using astro scopes for terrestial viewing? and on the above noted scopes in particular for replacing the spotting scope.

cheers
Jeelan

[Atmos (Colin)]

Being reasonably short triplet refractors they should perform really well for terrestrial viewing. As for hand holding them, they will be considerably heavier and more cumbersome to use than a spotting scope. They will be better performers but that does suffer at hand held usability.

[jeelan (Jeelan)]

hey Atmos,

I wouldnt hand hold the scope, but wouldnt be purchasing a astronomy tripod either.

My intention (at this stage) would be to use a standard spotting scope tripod with fluid filled head that has X and Y axis movement.

The only other thing is I'd need an erect image diagonal. I know this is done using a prism - does this compromise image quality at all for astro visual?

cheers
Jeelan

[Atmos (Colin)]

As long as you get the adapters and the tripod/mount head can take the weight it'll do fine.

As for the diagonal, I have no idea I'm afraid.

[deanm (Dean)]

Take the C11...!
Dean

[OzEclipse (Joe Cali)]

Originally Posted by jeelan

hey Atmos,

I wouldnt hand hold the scope, but wouldnt be purchasing a astronomy tripod either.

My intention (at this stage) would be to use a standard spotting scope tripod with fluid filled head that has X and Y axis movement.

The only other thing is I'd need an erect image diagonal. I know this is done using a prism - does this compromise image quality at all for astro visual?

cheers
Jeelan

Hi Jeelan

A Skywatcher/Orion ED80 tube weighs 3.5kg. It will sit on a midsize tripod like a manfrotto 090 with 041 head ok for terrestrial. This is the tripod at the small end of the professional range. For astro use, a taller stronger tripod is much better. On a small tripod, pointing up puts the eyepiece very low and awkward and balance and clearance of the tripod can become an issue when looking up. Using a large tripod - eg a Manfrotto 475 is much more comfortable. IF you put a Vixen dovetail clamp on top of the tripod and attach the tube with rings and a dovetail bar, you can re-balance in one axis and the mounting will be more secure. This arrangement will make balance around the elevation axis more of a problem.

A 70mm f6.2 refractor such as, william optic M71, stellar vue etc with 400mm focal length, will sit much better on a small to mid-size tripod for terrestrial and astro viewing.

Eyepieces, diagonals are interchangeable so you can get an erect image prism and a star diagonal for Terrestrial/astro viewing.

Alternatively, you can just use a star diagonal. If you stand behind the refractor facing the thing you are looking at and look down into the star diagonal, you will get an erect but mirror reversed left to right image. This is usually not an issue for wildlife viewing.

Joe

[jeelan (Jeelan)]

Originally Posted by deanm

Take the C11...!
Dean

LOL I'd need another trailer just for that thing!!


JOE - thanks for that. I was just reading up about image orientation in refractors. forgot that image is only swapped left to right but NOT inverted in refractors. The left to right i'm not that concerned about - it was more the inverted image that I wanted to correct.

I've got a Manfrotto 055CXB tripod and currently use a 488RC ball head for my spotting scope/DSLR etc.

Looking at the specs, the 488RC4 head has a capacity of 8kgs so plenty for an 80mm refractor + 2" diagonal and a decent 2" eyepiece.

Looking at the Orion ED80t CF at this stage.

cheers
Jeelan

[Renato1 (Renato)]

The only problem with what you propose is that your nice expensive 80mm telescope would be pretty useless for astronomy on your tripod at anything other than low power.

There used to be an easy solution, namely the Celestron Delux Slow-Motion control, which you'd attach to your tripod, and then attach the telscope to the slow motion control, with which it was easy to keep the telescope on an object at 180X. My fluid pan tripod would always slide when the telescope was aimed high, so I used a plain mechanical head tripod instead. Unfortunately, that slow motion control unit is no longer made.

Orion do make their version of the slow-motion control, and it is sold by Bintel. Unfortunately, it is nowhere near as good as the Celestron unit. It has an extra altitude feature which always slides with the telescope aimed overhead, no matter how hard you tighten the knob. I glued it shut with a piece of sand paper between the two surfaces to stop that feature working, which stopped the sliding. That worked, but the unit still vibrates a lot, so that when keeping the telescope on an object at 180X, I am forever adjusting the knobs to bring the planet to the edge of the field, then having to take my hands off and waiting for the vibration to die down as the planet crosses the field. So, it still works, but nowhere near as well as the sturdier Celestron unit did.

I don't know about the newest premium Erect Image diagonals, but the ones I have were premium in their time. They aren't as good for high power views on the planets as regular diagonal (some fine detail is lost), but they are usually fine for low power terrestial views.
Regards,
Renato

[Wavytone]

OP,

Keep a decent telescope for astronomy at night and use binocs by day, for two reasons:

1. Scopes are optimised for night time use in low light. By day with much more light you quite simply do not need the extra aperture - a good 40-50mm doublet is quite capable of giving sharp images at 50X - far higher power than you will ever use handheld or in a spotting scope.

2. Portability. You'll soon tire of lugging the extra weight and wish you had binocs instead.

It's much the same as the old DSLR vs compact camera dilemma - there's really no point using a DSLR if all you photos are only ever printed at A4 or smaller, displayed on computers or big screens.

[Max Vondel (Peter)]

Get an 8 inch dob...and get some decent eps!