Right Angled Finderscopes

[makeyourself]

Hi I've just got a Meade 4500 second hand and am having quite a bit of trouble with the finderscope due to having to put my head almost upside down to look through it which is causing headache and fatigue. I've been looking at right-angled finderscopes as a solution but as I'm quite inexperienced with telescope equipment I'm having trouble choosing. At the moment I only use the scope in my back garden where there is a fair amount of light pollution (I can only see stars of 3-4m with the naked eye). I've looked at reflex sights but I was thinking that, due to the light pollution and my inexperience, I could probably do with a magnified finderscope. So the ones that I'm considering so far are these:

http://www.firstlightoptics.com/finders/skywatcher-9x50-right-angled-erecting-finderscope.html

http://www.firstlightoptics.com/finders/celestron-illuminated-right-angle-correct-image-finderscope.html

http://www.telescopehouse.com/acatalog/info_07211.html

http://www.telescopehouse.com/acatalog/info_07212.html

Firstly I was wondering if somebody could tell me if any of these will actually fit a Meade 4500? Secondly considering the telescope that I will be using it with, am I better to go with a 9x50 or a 6x30, i.e. greater magnification or slightly greater FOV? Finally, something that's confusing me - it says the Celestron 9x50 has an apparent field of view of 5deg, surely this is a mistake?

[Cornelius Varley]

The finderscope on the 4500 is attached to the telescope tube by two thumbscrews whilst the SW 9x50 uses the standard Vixen mini dovetail. The Celestron finder is designed to fit on to an SCT so may not fit the Meade. The two Orion finders will be the same as the Skywatcher finders of the same size. To attach the SW / Orion finder you will need a new mounting shoe http://www.firstlightoptics.com/finders/finder-mounting-shoe.html and you might have to drill new holes to attach it to the tube.

[ottUp]

Don't know which of those will fit automatically, but certainly anything can be made to fit - at worst you might have to mount a new "shoe", drilling a couple of holes.

Of the finders you list in the links, a few general comments:

• They are all RACI finders (Right-Angle Correct Image), which means they use a prism instead of a mirror, which means the image you are looking at is correct - it's not reversed left-right.  That's important.  Cheaper mirror-based right angle finders add confusion to an already confusing geometry.
• I'd go with the 9x50 not the 6x30.  The extra aperture will give you a slightly wider field and, more important, a slightly brighter image.  You'll need both if you're trying to see targets directly in the finder (as opposed to star-hopping, in which case it's slightly less important).
• The Celestron has an illuminated reticle, which is a very nice extra.  If you are under good dark skies, it can be hard to see the black cross-hairs in a finder, and the illumination really helps.  If you have heavy light pollution, your skies won't be truly black and this is less important.  If you go with the illuminated finder, buy extra batteries.  You will forget to turn it off.
• The 5-degree field sounds about right.  My 8x50 Stellarvue finder has a 6-degree field.  The circles in a Tetrad are 0.5, 2, and 4 degrees.

Regards

   Richard

[Mr Spock]

I use the Celestron 9x50 RACI and it really good for finding faint stuff.

[makeyourself]

• I'd go with the 9x50 not the 6x30.  The extra aperture will give you a slightly wider field and, more important, a slightly brighter image.  You'll need both if you're trying to see targets directly in the finder (as opposed to star-hopping, in which case it's slightly less important).

The one with the widest reported field of view is actually the one with the smaller the aperture, the 6x30 Orion at 7 degrees. Compared to the 9x50s which are all 5-5.6 degrees. So I'm not sure which out of FOV and magnification would be more important, maybe 5 degrees is quite wide anyway?

I found a shoe for the Orion ones and the Skywatcher that says it will fit Meade telescopes:

http://www.scsastro.co.uk/catalogue/orion-dovetails-for-finderscopes.htm

I also a found an equivalent to the Celestron which will fit the same shoe:

http://www.scsastro.co.uk/catalogue/orion-9x50-illuminated-right-angle-ci-finder-scope-7020.htm

But if I did decide to go with the Celestron, what type of shoe exactly would I need for that?

[glowjet]

This is not going to be an easy solution, The Celestron RACI is a complete unit having its own dovetail mounting bracket. The existing finder scope on the Meade appears to be mounted on two studs fixed in the body of the scope. This going to cause you problems, as I doubt there is anything on the market that can convert one to the other. If you have DIY skills, or know someone who has, a purpose made plastic/alloy mounting block could be constructed to fit the existing studs, the block then drilled to accept the new Celestron bracket.

If would also draw your attention to the many commercial accessory mounting shoes, available to purchase for various finder scopes, all the mounting holes are on the inside of the units, studs and nuts may well interfere with any dovetail mounting foot of the scope, even if the holes do match the stud centres.

The ruthless alternative is to remove the existing studs, if possible, drill the scope tube and fit the base of the finder scope of your choice. Or, simply just remove the existing scope, leave the studs and fix your scope and base using good strong double sided tape. Hope you find a solution

[Ju Piter]

hi fitting a RACI finder is easy i had the same problem with my 130p so just drilled 2 holes fitted the shoe attached the finder job done

[makeyourself]

Thanks for all the replies so far, if a commercialised shoe is not available for the Celestron then I would probably avoid that option since there is an alternative available. I would really prefer not to drill into the telescope if I can avoid it as I'd be worried about damaging it but would do so as a last resort.

I have actually just checked to compare the fittings with a Celestron Powerseeker 127EQ that I also own and the finder scope fitting is almost identical to the Meade 4500. The studs are both 2 centimetres apart and the nuts are interchangeable so the studs must also be the same diameter. But for some reason if I try to switch finder scopes they won't quite fit, I'm presuming it's just because the 127EQ and 4500 are different diameters. But basically the 4500 would seem to have some kind of standard 2 stud fitting if that makes any sense at all! So I'm hoping that one of these types of brackets/shoes will fit without having to drill since they claim the bracket will cover all diameter telescopes. Please let me know if I'm not making sense since still finding this all a bit confusing! Here's a photo of the studs on the 4500:

But anyway at the moment I'll be going for one of the Orions or the Skywatcher on the basis that I can use that bracket.

[glowjet]

The finder scope bases, with the exception of the Celestron, have a die cast open foot to the standard shape of the vixen fitting. As I mentioned in the second paragraph of my thread, although the shoe has a hollow base to fit a variety of scope tube diameters, the fixing to the scope is through holes on the inside of the shoe, which means although you may find one with holes to fit the existing 20mm stud spacing, the nuts and studs are likely to interfere with the passage of the foot of the finder scope.

If you take note of the shape of the vixen foot, it has sloping sides and a flat top. Some information for you, taken from one of my own. It is 30mm overall across the base, 25mm internal. 10mm high overall 8mm internal at the centre. From this it may reasonably be assumed that the foot may well clash with the studs and nuts when the shoe is fixed to the base. Hope this makes things a little clearer for you.

[pevsfreedom]

I love my RACI 9x50. Trick is learning to orientate your star atlas to the RACI view. Usually I find objects without even looking at the sky, just the atlas and the RACI. 

[makeyourself]

Thanks for the additional info and sorry for the late reply, not been on here for a few days. I went for the Orion 9x50 non-illuminated version in the end. Was surprised at how big and heavy it was but it seems of stearn build quality and the image produced is fantastic.

Glowjet, you were exactly right about the nuts on the existing studs interfering. So I removed them, took the screws out and replaced them with countersunk screws inserted from the top. That solved the problem and worked perfectly. I used this shoe which I would recommend if someone is looking to use existing holes on the telescope due to the fact it has 8mm wide rails for screws to fit into:

http://www.telescopehouse.com/acatalog/info-BC202.html