Finderscope for ST80mm

[mark81]

Hi All,

So I have been upgrading my Skywatcher St 80mm, so far I have bought a BST 12mm and the 8mm and now I am thinking about the red dot finder.  I know some people love these things but I cant seen to get the hang of it.  Too much time being spent moving my head here and there - seeing the red dot and then it vanishing again - maybe I will get the hang of it.. but my question is if I got a standard viewfinder is the 6x30 any good?  I am guessing the 9x50 is a step too far considering that the scope os only an 80mm... what would you do?

Many thanks

Mark

[michael.h.f.wilkinson]

Why not get a wide angle EP, something like the MaxVision 68 deg 24mm. That gives a 4.08 deg FOV and should act as an effective "finder", and gives beautiful wide-field views as well.

[Dazzyt66]

+1 for a large ep. I used to have a red dot on my ST80 but can quickly find stuff using my 30mm Vixen or my 40mm revelation (which is up for sale atm) as their FOV good. HTH ?

[Davey-T]

I had an ST80 that came with a teeny finder scope and as mentioned it was easier to find stuff using long focal length eyepiece than using the supplied finder.

Dave

[andrew63]

Nothing wrong with the standard 6x30 finder, that are usually supplied with the telescope - I use one all the time.

 

andrew

[JAO]

Agree with the comments about a wide field eyepiece but a 6x30 finder is also a nice basic tool. I really like red dot finders as well though and it took me a while to get the hang of them, but it was with the effort. They are particularly good if you know where the object you want to see is in the sky. An optical finder is probably better if you are uncertain about an objects location and need to be able to confirm through some magnification. Hope this helps.

[michael.h.f.wilkinson]

I have a straight-through 6x30 finder on my C8, and got a 6x30 RACI (right-angle, correct image) finder for my kids' mini-Dob. RACI finders are clearly easier than straight through types, and the one on my C8 is only ever used at the start of the session to align the 14x70 RACI finder I made to the scope. After that, I only use the 14x70 finder. That would be overkill for an 80mm scope, I admit, but on the C8 it is a gem

[happy-kat]

Another one using a large fov eyepiece rather than a finder in my ST80. There's a couple choices for sale at the moment on here. 

[billyharris72]

Personally, I'm not convinced of the value of an optical finder on an ST80, though others clearly do find it useful. A simple red dot finder, if you can get the hand of it, is of use, but I'd agree that a wide field eyepiece is probably the best option. I actualy aquired an erect image diagonal for the purpose (cheap, off astroboot) but to be honest I never really use it these days.

Billy.

[Louis D]

Try using a momentary green laser sight or a green laser pointer shining into your eyepiece to do a quick, rough alignment of your scope on the sky.  As I've aged, I find it difficult to contort myself to look through a unit power finder above 60 degrees elevation or so.

[happy-kat]

The use of lasers is really not a good idea to suggest, this is particularly true for the UK.

[Geoff Lister]

I also found the standard RDF difficult to use at high altitude angles, so I added an optional 45 degree mirror, deflecting the view by 90 degrees.

The rear of the RDF and the wooden offcut mirror holder each have a 10mm dia, 1mm thick, rare-earth magnet. I found that a 40mm square acrylic mirror tile works well, and the magnets hold the mirror assembly (roughly 16 grams) like a limpet on a rock. The 40mm size tile shows a reasonable chunk of sky around the sides of the RDF's sight-tube. By adjusting the slope of the wooden block, it is possible to throw the view towards the eyepiece; reducing the head movement needed when aligning. The 30mm square and 30mm dia mirrors also work, but I found the 40mm square the best compromise size/view.

Geoff

[Louis D]

31 minutes ago, happy-kat said:

The use of lasers is really not a good idea to suggest, this is particularly true for the UK.

Here's a CN thread on this very topic of green laser pointer legality, at least in the US, though the same concerns apply worldwide.  I have green laser sights mounted on picatinny rails on my 8" dob and on my grab and go mount.  I was using one just the other night alternately with my Telrad.  There was even a plane nearby that I waited for it to pass by before lighting up.  No men in dark suits have shown up at my doorstep to arrest me yet.

[mark81]

thanks for all your comments and suggestions! This is such a great site...

[JAO]

17 hours ago, Geoff Lister said:

I also found the standard RDF difficult to use at high altitude angles, so I added an optional 45 degree mirror, deflecting the view by 90 degrees.

The rear of the RDF and the wooden offcut mirror holder each have a 10mm dia, 1mm thick, rare-earth magnet. I found that a 40mm square acrylic mirror tile works well, and the magnets hold the mirror assembly (roughly 16 grams) like a limpet on a rock. The 40mm size tile shows a reasonable chunk of sky around the sides of the RDF's sight-tube. By adjusting the slope of the wooden block, it is possible to throw the view towards the eyepiece; reducing the head movement needed when aligning. The 30mm square and 30mm dia mirrors also work, but I found the 40mm square the best compromise size/view.

Geoff

Geoff,

That's a really neat mod. I have a mirror on my TV Starbeam but your mod is simple and very cost effective, nice work!

[Cosmic Geoff]

I have a Sky-watcher Startravel 102mm achromat, a size bigger than the ST80.  It has a red dot finder on it.  I have a 6x30 finder and a 9x50 finder that I could swap onto it in moments, but I have never found any reason to do so.  IMHO the red-dot is a widefield finding device, and matches with a widefield telescope.

[Geoff Lister]

5 hours ago, Cosmic Geoff said:

IMHO the red-dot is a widefield finding device, and matches with a widefield telescope.

I would agree, but in addition, on a Newtonian or OTA with a 90 degree star diagonal, it is useful to have the option of throwing that view in the same plane as the eyepiece, particularly at the higher altitude angles. However, the 6x30 and 9x50 finders do not suffer from the RDF's perennial problem - a flat battery .

Geoff

[Louis D]

2 hours ago, Geoff Lister said:

do not suffer from the RDF's perennial problem - a flat battery

I'm still using the original CR2025 cell that came with my Rigel QuikFinder 18 years ago.

[25585]

On 12 April 2018 at 12:41, michael.h.f.wilkinson said:

Why not get a wide angle EP, something like the MaxVision 68 deg 24mm. That gives a 4.08 deg FOV and should act as an effective "finder", and gives beautiful wide-field views as well.

40mm Plossl is what I use. 10x magnification. Tele Vue. Other makes abound for that focal length. 

[michael.h.f.wilkinson]

17 minutes ago, 25585 said:

40mm Plossl is what I use. 10x magnification. Tele Vue. Other makes abound for that focal length. 

Works, but the 24 mm 68° option gives the same FOV, with a much more useful exit pupil of 4.8 mm, rather than 8 mm for the 40 mm Plössl.

[25585]

5 minutes ago, michael.h.f.wilkinson said:

Works, but the 24 mm 68° option gives the same FOV, with a much more useful exit pupil of 4.8 mm, rather than 8 mm for the 40 mm Plössl.

Are they not quite heavy for a small scope? A 32mm Plossl gives same FOV but more magnification as the 40 (but with less eye relief).

[happy-kat]

You can hang a dslr off them so I'd expect the 24mm maxvision would be fine.

[Stub Mandrel]

The problem with the 9x50 finders is they are actually lovely little wide field scopes to look through! I use one as a finder when doing AP and it's surprising what you can see through one.

[xvariablestarx]

What about a Right Angle, Correct Image type finder, or would that be too bulky for your scope?