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Proper RACI finder or 70mm Travelscope


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Hello all, 

Since purchasing the Skytee and TS102 F7 ED, I find myself in need of a finder, as I am not enjoying swapping out EPs multiple times when trying to locate objects. I have a skywatcher 50mm but it is straight through, so using it near the zenith is not comfortable for me. I also remember never really enjoying the red dot finder on my old Skymax 102 and my skies can only show me the very brightest stars in a given constellation, so I'm not sure if a zero magnification finder is where I want to go either. 

As I see it, that leaves me with two options to consider: Either a 50mm RACI type finder OR to set up my old Celestron 70mm Travelscope + low power EP. on one of the other mount points of the Skytee.

As I understand it from reading elsewhere, the 50mm finder will show me about 5.5-ish degrees of sky, whereas with the Travelscope and a 32mm Plossl I can only manage 4deg.

The finder option is simpler but does require buying (at least) the finder, plus although my TS102 has a finder shoe, I'd prefer to mount it direct to the Skytee, so more bits and pieces are needed. I can put together the travelscope version with stuff I have already (except the 32mm Plossl - I do have a 24mm SWA which shows roughly the same TFOV.) plus it's a bigger aperture, real EP instead of the finder ones which feel like they're going to poke your eyes out, and it feels a bit more fun. 

Anyway I would love to hear opinions or experiences of others with simar setups! The main concern really is whether the travelscope version would actually perform its function as a finder well enough, I suppose. 

Of course I *could* use my ZS73 plus Panoptic 41mm as a finder but that seems extreme 😂

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Thanks all. A lot of love for the RACI! To be honest I'm not *against* the idea at all, it's just that I will have to purchase the RACI plus some other bits to make it work, and feel like having the 70mm scope sat around doing nothing feels like a waste. 

I do like the look of some of the mentioned finders; I was also looking at the TS 50mm finder which seems to get quite good feedback. 

Maybe it's worth me setting up the travelscope anyway as a test (it won't cost me anything after all) and seeing how I get on? I've also seen that SVBony do a 0.5x focal reducer which is an interesting prospect - with an 18mm BST that I have already I would get 5.4 degrees of sky and a 6.3mm exit pupil! 

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I use a 50mm RACI with an RDF for my ZS66. The finder is hardly smaller that the main scope, but is much wider and corect image. It takes eyepieces and I use either a Super 25 or an ES 20/68 giving 6-7 degrees. I absolutely love the combination, so much I wrote a book for my RACI!

Regarding the finder, the 50mm aperture is the least important part of it, the most important thing is the correct image. I can't mentally flip and rotate star fields at 1 AM. 

Edited by Ags
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21 hours ago, Ags said:

I use a 50mm RACI with an RDF for my ZS66. The finder is hardly smaller that the main scope, but is much wider and corect image. It takes eyepieces and I use either a Super 25 or an ES 20/68 giving 6-7 degrees. I absolutely love the combination, so much I wrote a book for my RACI!

Regarding the finder, the 50mm aperture is the least important part of it, the most important thing is the correct image. I can't mentally flip and rotate star fields at 1 AM. 

Agreed, the main use case for me is the correct image. Since returning to a non-goto mount I have spent a reasonable amount of time faffing about with charts, trying to mentally flip star fields and it is not much fun.

I do have an amici prism diagonal knocking about somewhere which I would use with the travelscope if I went down that route, but I have a feeling it strangely has a smaller aperture somewhere in the light path which would cause vignetting at low power. 

I believe you have the TS finder - the one in your profile image? 

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I don’t see why the 70mm shouldn’t work well as a finder. I’ve used an 80mm Lumicon finder before and currently have an Altair 60mm one. The benefit is that the greater light grasp allows you to actually spot targets which might be beyond an 30 or 50mm. The downside is the potentially narrower field of view.

Assuming you have an erecting prism then I think it is worth a go, and the 24mm should work just fine. Used with an RDF or Telrad they do make a very quick and easy way of finding targets; roughly point with the Telrad then refine position with the finder.

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3 hours ago, Mr Spock said:

My current 102mm finder configurations:

9x50 RACI and RDF
1760295032_DSC_0169_DxO1200.jpg.195bf658b4f6d541e9ae1d0c9e568e80.jpg

Solar (other finders removed for safety)
190470201_DSC_0160_DxO800.jpg.5437c1f3f2f4fde052998baeeca2837a.jpg

Thanks for the pictures, very helpful to see the different setups! I like the lower profile of the RACI mounting. 

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3 hours ago, Stu said:

I don’t see why the 70mm shouldn’t work well as a finder. I’ve used an 80mm Lumicon finder before and currently have an Altair 60mm one. The benefit is that the greater light grasp allows you to actually spot targets which might be beyond an 30 or 50mm. The downside is the potentially narrower field of view.

Assuming you have an erecting prism then I think it is worth a go, and the 24mm should work just fine. Used with an RDF or Telrad they do make a very quick and easy way of finding targets; roughly point with the Telrad then refine position with the finder.

Thanks Stu. I had a quick go with it and the 24/68 earlier in the daytime and not sure I could see any vignetting, so I might give it a go and see what happens, I don't have anything to lose I guess! 4deg. of sky is not loads for a finder but it will stop me needing to switch EPs at the very least.  I'll report back how it turns out. 

If it doesn't work out I will perhaps investigate the dedicated finder option!

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  • 1 month later...

Hello all, 

Quick update on this. I finally got to do a limited amount of testing and it worked okay, but ultimately I have decided a RACI will be a better option. 

As mentioned, I can only ever get a maximum of about 4° of sky with the travelscope, which is okay but I'd prefer to have the option go wider. According to my calculations a theoretical 7.8° could be possible in the RACI finder with the same EP as above, although I suspect that might not work in practice. 

It's also a bit more flexible having a finder shoe, as I can use it on multiple telescope setups and not only on the Skytee-2, although I imagine will construct an adaptor with a vixen dovetail at the bottom and a synta/vixen finder shoe at the top so I have lots of different mounting options. 

 

Anyway, thanks for all the input as always! 

Edited by badhex
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