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iPeace

I'm sure someone has tried this...and now I will

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Picture the amateur astronomer. He's (yes, in this case, it's a male) sometimes still faffing about, hasn't quite got the finder thing completely sorted - he's managing, and having fun, but... well... He's got an RDF, he's got a Rigel, he's got a nice 9x50 illuminated RACI. He wishes the RACI were a bit, well, more 'mucho', as bino use has gotten him star-hopping in correct-image mode, and he feels that is probably the route he should take. He's got an Ercole mount, he's got a TS INED70, he's got a TV Panoptic 41mm to use besides his other scope(s).

Soooo....add a nice Baader 2" Amici Prism Diagonal, and what do you get? An effective upgrade from the 9x50 RACI?

  • The RACI provides 50mm aperture with 9x magnification and 5° TFOV.
  • The combination of TS INED70, Baader 2" Amici Prism Diagonal, and 41mm Panoptic provides 70mm aperture with over 10x magnification and over 6.2° TFOV.
  • Stick the new combination on the Ercole, opposite the main observing scope...the RACI is replaced?

Is the amateur astronomer overlooking anything in these considerations, or is it a plan?

There is, of course, the question of whether any but the most (prohibitively?) expensive amici prisms will deliver performance suitable for astronomy; but keeping in mind this is meant to 'merely' be a replacement for a Synta 9x50 RACI, could an offering from Baader be expected to deliver a worthwhile improvement (in combination with the other named components)?

In any case, the Baader model BA2956152 is incoming, and the amateur astronomer will be more than happy to share his future experiences.

To be continued.

:happy11:

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I think it's a good but somewhat expensive plan. Last year I had a Mini Borg 60 and Baader Amici prism, which I took great pains to align with my long fracs on my Skytee, but it worked very well indeed. I found myself using it as a standalone scope quite often....:smiley:

BTW, the Baader Amici prism is very high quality and perfect for astro use- another item I shouldn't have sold.

Edited by Roy Challen
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I've been down this route before, and it does have some merits. The main problem you might face is getting a satisfactory alignment between scope and 'finder'. You can adjust the two axes of the Ercole in altitude accurately enough, but if there is any error in azimuth it is difficult to correct, without resorting to guidescope rings, or an adjustable guidescope mount.

I seem to enjoy the masochistic art of creating and building different finders. I built a couple from an old pair of 80mm binoculars a while back, complete with cheap amici prisms and mounted on guide scope rings. Optically they were uncouth, but they did the job.

My latest has just been refined tonight. It is the patented Mega RACI finder with built in (or rather 'stuck on'!) TelRad! Actually it's not so much patented as so unique that I doubt anyone else would copy it ;)

It is basically a Lumicon 80mm finder scope with amici prism and a 25mm reticule eyepiece, not yet illuminated. That is a good point actually, don't forget the possible need for a reticle eyepiece. This is likely to mean a shorter focal length eyepiece but actually being able to centre targets is quite useful ;)

I'll add a picture or two soon!

EDIT I didn't say they would be good pictures ;)

In theory, this could also bolt into the other side of a dual sided giro type mount, anything from a mini girl to an Ercole.

image.jpeg

image.jpeg

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Excellent insights, thanks!

I have seen two 2" amici prisms available from Baader, one of which they claim is "astro quality" - I have ordered the other one, which I hope will do well enough for this purpose.

:happy11:

During my trial runs, the alignment of my Ercole seemed promising enough on both axes to let me invest in this.

As for a reticle eyepiece, yes I have enjoyed that feature of the RACI... So in the end, I may keep using it as well... Point with the Rigel, find and star-hop with the INED70, center with the RACI, observe with main scope. Perhaps not for grab-and-go nights...

Much of the attraction for me is in the extra FOV that the 41mm Panoptic gives (in combination with the f/6 INED70, of course) over the RACI so I wouldn't gladly give that up for crosshairs, illuminated or not. I'd sooner use the RACI as well, atop the main scope as a utility finder for centering only.

Stu, your creations are always wonderful - at least the ones you show us are - and this one is equally great!

:icon_biggrin:

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On 08/28/2016 at 00:25, Stu said:

I've been down this route before, and it does have some merits. The main problem you might face is getting a satisfactory alignment between scope and 'finder'. You can adjust the two axes of the Ercole in altitude accurately enough, but if there is any error in azimuth it is difficult to correct, without resorting to guidescope rings, or an adjustable guidescope mount.

I seem to enjoy the masochistic art of creating and building different finders. I built a couple from an old pair of 80mm binoculars a while back, complete with cheap amici prisms and mounted on guide scope rings. Optically they were uncouth, but they did the job.

My latest has just been refined tonight. It is the patented Mega RACI finder with built in (or rather 'stuck on'!) TelRad! Actually it's not so much patented as so unique that I doubt anyone else would copy it ;)

It is basically a Lumicon 80mm finder scope with amici prism and a 25mm reticule eyepiece, not yet illuminated. That is a good point actually, don't forget the possible need for a reticle eyepiece. This is likely to mean a shorter focal length eyepiece but actually being able to centre targets is quite useful ;)

I'll add a picture or two soon!

EDIT I didn't say they would be good pictures ;)

In theory, this could also bolt into the other side of a dual sided giro type mount, anything from a mini girl to an Ercole.

image.jpeg

image.jpeg

This raises a question I would like to put to you. I have trouble using a Rigel to sight targets near the zenith; I can't get down low enough behind to get proper aim. I feel I must be overlooking something...

What sort of posture do you assume when using a Telrad to sight targets near the zenith?

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Hmmm, you may have hit on something there! If you have the tripod set low enough to observe sitting down, then the position is roughly along the lines of grovelling in the mud.

My problem is that my back does not allow me to stand for any length of time, otherwise I would have the tripod set higher which would make life easier.

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1 minute ago, Stu said:

Hmmm, you may have hit on something there! If you have the tripod set low enough to observe sitting down, then the position is roughly along the lines of grovelling in the mud.

My problem is that my back does not allow me to stand for any length of time, otherwise I would have the tripod set higher which would make life easier.

I too prefer observing in a seated position, makes it easier to keep still at the eyepiece. So there remains the question of how to use a Rigel/Telrad towards the zenith. I wonder how others do it? I haven't yet tried a sideways position, one ear on scope, I suppose because it didn't occur to me - or just isn't natural. I wonder how high I could raise the finder up above the plane of the scope before it would fail to align sufficiently? One sees risers for the Telrad for sale with a height of 10cm.

Short of constructing a full-on swivelling AAA-battery-type platform for seat and scopes on which the observer reclines, how do these popular devices actually get used?

:huh2:

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Well, fo me, I tried all sorts of finderscope configurations, until one night I saw the light. And the light was red.

I now use a Telrad on all of my scopes (or for ease of travelling a simple red dot) and a set of Telrad charts. I find it so much simpler than star-hopping, although to an extent it is a form of star hopping!

You can get riser platforms to increase the distance the Telrad is from the OTA. You can also get 90-degree image reflectors (?) that make it easier to use near the zenigh. For me, I simply kneel down and contort, but I know that may not be as easy for some people. You can even get dew shields and heaters for Telrads! 

Oh, and you don't have to mount the Telrad up back near the focuser! That's what makes it problematic when viewing the zenith! Mount it near the altitude axis on the OTA, or even further forward - that gives you a bit more leeway to view along/through it.

So my advice, and it's only based on my preferences, is to look at how the Telrad can be kitted out and see if there's a solution there that will make it usable for you.

Ant :)

 

PS another option is not to observe near the zenith. I find it tricky with alt-az mounts, and you can always observe other objects while waiting for things to reach easier positions to view.

 

Edited by A McEwan
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2 minutes ago, A McEwan said:

Well, fo me, I tried all sorts of finderscope configurations, until one night I saw the light. And the light was red.

I now use a Telrad on all of my scopes (or for ease of travelling a simple red dot) and a set of Telrad charts. I find it so much simpler than star-hopping, although to an extent it is a form of star hopping!

You can get riser platforms to increase the distance the Telrad is from the OTA. You can also get 90-degree image reflectors (?) that make it easier to use near the zenigh. For me, I simply kneel down and contort, but I know that may not be as easy for some people. You can even get dew shields and heaters for Telrads! 

Oh, and you don't have to mount the Telrad up back near the focuser! That's what makes it problematic when viewing the zenith! Mount it near the altitude axis on the OTA, or even further forward - that gives you a bit more leeway to view along/through it.

So my advice, and it's only based on my preferences, is to look at how the Telrad can be kitted out and see if there's a solution there that will make it usable for you.

Ant :)

 

Indeed, love what my Rigel does, have even mounted it up past the alt axis, but still find myself down and contorting, so I will indeed continue to develop a solution for this - may even 'upgrade' to a Telrad as well. To be continued!

:happy11:

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It's a good plan. I use an ED 80 with a 21mm Ethos giving x23 and 4.4 degrees TFOV as a finder. I could get wider fields with a longer FL eyepiece but I find x23 gives better contrast and thus shows targets better. 

 

Interesting note: I do this on my Ercole too,  but I've found it easier not to use a RACI  finder on this set up. I think it's because having the two sides of the mount being flipped left to right is confusing.

Edited by Commanderfish
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Well, this plan had first light on Wednesday night, when I tried it out without a "main scope", so just the "finder". The Baader amici prism is very nice indeed; makes me wonder how much better their "astro quality" amici prism actually is...if it's significantly better, I'd be very impressed! Basically, it's like using a big mounted monocular, and the views are great! So last night (Thursday) I went for the full setup with the TS INED70 / Baader amici prism / TV Panoptic 41 opposite the SW ED120. I mounted the Rigel finder up past the mount, and the illuminated RACI on the ED120. I have now solved the problem of using the Rigel near the zenith; I just stand up against the extension pillar and bend down a bit; this gets me a lot closer to the Rigel when sighting, but it works great! So: use the Rigel to get in the neighborhood, use the TS INED70 in RACI mode to get the target roughly centered and enjoy the "preview", switch to the ED120 to observe at the selected magnification; use the RACI on the ED120 as necessary for extra fine alignment - has not really been needed, as of yet. The RACI-ness of the INED70 with the Baader amici is great for navigation following charts, etc. It's just like using binoculars to find stuff, which I find fun and intuitive.

This is working very efficiently, now; I was zipping around the sky, finding, aligning and observing with no faff at all. It's taken me a while... :rolleyes2:

Do still need to get the dew issue sorted in a structural manner. Will go to great lengths not to have to use heaters... :happy11:

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