Best Finder in Light Polluted Skies

[ONSLOWE]

I need a finder for my scope (currently only an 80mm F11 refractor) and was looking for recommendations. I have bad light pollution and street lighting / security lights nearby and think that would make a red dot finder less effective, tried a Telrad years ago on a different scope and did not find it ideal. I think a right angled finder might suit me best, has anybody tried a 6 x 30 erect image finder or the Skywatcher 8 x 50 version. I would look to keep the finder if I upgrade the scope. I have tried star hopping in the past but the light pollution does not do me any favours.

Thanks,

[kniclander]

I have used skywatcher 6x30 and 8x50 straight thru and 6x30 and 8x50 right angled - the 6x30RA was up down corrected and the 8x50 was up down and left right corrected. Here is a mini review -

6x30 straight through - pants view cricked neck impossible to star hop cos everything is upside down etc

8x50 as 6x30 except the view is very very good

6x30 right angled - terrible view (worse than pants) say no more

8x50 right angled - beautiful in all respects (although the view is slightly less good than the 8x50 straight thru)

ps my skies are really LP'd

HTH

Dan

[russ]

The 9x50 RA is a nice finder, i have the Orion USA version. Clear and bright, nice sharp stars. Can't really fault it. Except it's too heavy for my dob, so i end up using a 6x30 straight through. I do find the crosshairs hard to see sometimes in both finders.

So to cure both my problems i have ordered the Orion USA 8x40 straight through illuminated finderscope. Strangely the Orion version of the Synta illuminated finder is a lot cheaper than the Skywatcher version and looks a whole better in black.

[scotastro]

An 8x50 (or 9x50) finderscope with a right way up image certainly makes finding objects a lot easier for the beginner. The large aperture gives brighter star images making locating object easier.

Illumination of the cross hairs is not necessary of you have light pollution.

Mike

[TheThing]

Tal do an excellent 8x50 finder if you can find one. Or the orion 6x30 is very good too.

[acey]

I still use the original 6x30 straight-through finder that came with my dob when I got it in 2000 - I've tried 50mm and 80mm finders but for dark-sky observing I don't need that extra aperture. Light polluted sites are a different story - from my back garden there's not a lot to see through the 6x30 finder.

However there's the question of what you're targeting. Faint galaxies just aren't an option from a light polluted site. I've managed to find bright DSOs like the Eskimo nebula, Dumbell, M81/82 etc from my light-polluted garden using the 6x30 finder, not to mention the loads of easy clusters up there like NGC 457, double cluster etc. I wouldn't waste my time trying to see anything much harder. All of those are visible with an 80mm scope - though a filter would be pretty much essential for the nebulae.

So personally, given that it's only an 80mm scope, I'd go for a 30mm finder - that's what I have on both my 8-inch and 80mm scopes. Whether it's straight-through or right-angle is a matter of taste. My own taste is for straight-through and I just get on my hands and knees when necessary. I'f I'm going to be looking at right-angles I figure I may as well be looking through the main scope.

In fact, if you don't like straight-through aiming, you could even ask whether a finder is really necessary - you might get by with a low-power eyepiece. If it has a 2-inch focusser then you could use a 55mm Televue Plossl to give a magnification of 16 and a field of view of 3.1 degrees. By comparison, an 8x50 finder would give you around 5.4 degrees, a 6x30 finder about 7. So you get less field but still enough - I have 15x70mm binoculars with a FOV of about 4 degrees and I have no trouble finding Messiers with them hand-held.

If your focusser is 1.25 inch then you wouldn't be able to get quite such low power - I think your lowest possible would be with a 40mm eyepiece giving a magnification of 22 on your F11, and a FOV of 2.3 degrees. In that case you really need a finder.

Some people might of course suggest you get a Nagler/Panoptic/Ethos etc etc in order to have a huge field of view but I'm assuming your scope cost less than £1000.

If you're thinking in terms of a finder that you'll keep when you upgrade the scope then why not upgrade now?

Andrew

[lunator]

Hi Onslowe

I obseeve under very LP skies, and have used a 30mm & 50mm finder.

I have found the 50mm finder on the OMC makes a significant diference in mu ability to track down objescts.

Cheers

Ian

[acey]

One other little point I'd add - I found that far more important than changing the finder was having a decent star map (SkyAtlas 2000).

In light polluted skies with a limiting magnitude of 4.5, a 6x30 finder will potentially show stars down to about magnitude 8 (less in practice because your eye can't properly dark-adapt). SkyAtlas goes down to 8.5 - so you can steer very close to the object you're looking for (ie to the nearest mag-8 star).

[John]

I use a GSO 8x50 right angle correct image finder on my 8 inch dobsonain and I find that it works well although I still tend to prefer a red dot finder as my skies are not too light polluted.

John

[russ]

I do prefer the straight through and quite like the 6x30 funnily. The right angle finder doesn't seem natural. My other problem is my north sky is quite dark and the crosshairs just disappear against the sky. Then there's the dew. So after 15-30mins i have to sight along the tube anyway. The red dot finder doesn't help either. What i would really like is a finder with built in dual heaters (front and rear) and illuminated crosshairs. Not asking much

[acey]

I can never see the cross-hairs against a dark sky but I don't find it a problem - I only need to get close enough to the centre to know what field I'll be seeing in the main scope.

To prevent the finder dewing I find a cardboard dewshield perfectly adequate - without it, the finder dews very quickly. I've never had the eyepiece dew - if it ever happened I would suspect it was due to my having accidentally breathed on it.

[russ]

Didn't even get a chance to use the finder before it went this morning. Setup the scope, then had to go back in for 10mins as my youngest woke up, came back out and both ends of the finder were dewed up. Not too mention the main objective on the ED80. So gave up and just used the 12.5 dob.

[TheThing]

You might find this helpful?

[TheThing]

Or this one?

[ONSLOWE]

Thanks for all of the advice and links, looks like the 9x50 is a winner so I will try to sort one out in the near future. In reply to Acey I can't upgrade the scope at the moment as I have just blown my budget on a PST for Xmas so the night time scope will have to wait. All the best for Christmas and the New Year to everybody, lets hope we can celebrate with clear skies.

Regards

Martin