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Illuminated Finder scope or Eyepiece?


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So my finder scope on my C90 is basically useless with it mounted in my sky-watcher mount. So I'm thinking of getting an illuminated finder scope to mount on my C90 so I can use it better. But I have also seen illuminated eyepieces (12.5mm). Does anyone have any ideas which would be better or both? I was looking at one of those Telrad scopes but it seems kind of big. Advice on the Telrad also. 

Thanks, Bobby

Edited by bsshog40
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I believe you have the Red Dot Finder (RDF) in mind? A device helping you to point the telescope?

Telrad is the best investment you can do for that. As the rest of similar products has a lot of flaws and deficiencies at about the same price range. While an illuminated eyepiece is not helpful at the pointing task at all.

The C90 OTA is indeed not big, but I believe Telrad would fit it out of the box using included sticky tape on its mount cradle. It's big on purpose to amend cheap optics issues other RDF devices have. Just select the location opposite to the declination axis of your SW mount head to avoid any interference with its motion. You can point with Telrad directly in a trivial RDF manner from any eye distance from it or employ advanced techniques, such as the TPM.

Another option to consider is moving the optical finder from the OTA to the counterweight arm of your GEM. Or just move it closer to the eye as the stock one I see on images is a straight through, so it shouldn't really be too bad on any GEM if mounted properly. If you are using a prism, consider upgrading to the RACI optical finder (also with the prism).

Edited by AlexK
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Thanks for the info Alex. I was thinking of using the illuminated eyepiece during alignment. Thinking after finding the stars, I can best center them in the eyepiece and get a more accurate alignment. 

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I use both a RACI illuminating dual crosshair finder and the same type 12mm EP in my main scope. I found the stock finder on my C90 almost useless, and even a hinderance during stellar alignment. The uber thick single crosshairs in the straight through factory finder are so thick they cover Vega, and many other pinpoint targets, when centered. 

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Just defocus a bright star and center the circle on the now backlit crosshairs of the reticle.  There's really no need for an illuminator in an eyepiece if all you're doing is centering on bright stars for alignment purposes.

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3 hours ago, Louis D said:

Just defocus a bright star and center the circle on the now backlit crosshairs of the reticle.  There's really no need for an illuminator in an eyepiece if all you're doing is centering on bright stars for alignment purposes.

The same trick is working for the accurate alignment through the telescope as the eye detects concentricity (this time with the edge of the FOV) better then centrality. So, don't hesitate to defocus it until the star donut is barely visible but almost reaching the field stop (a cheap narrow FOV EP, which is often just dusting in the EP box, will finally find the purpose! Been doing that with my ETX-125 all the time). The illuminated reticle EP is fun to play with though. And, if you are into the science even a little bit, is a must have for celestial measurements (drifting method).

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17 minutes ago, AlexK said:

The illuminated reticle EP is fun to play with though. And, if you are into the science even a little bit, is a must have for celestial measurements (drifting method).

Like the 12.5mm Celestron Microguide Ortho and 12mm Meade MA Astrometric?

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1 hour ago, Louis D said:

Like the 12.5mm Celestron Microguide Ortho and 12mm Meade MA Astrometric?

Exactly. CMO and MMA are even better for quick measurements. I'm using Meade 4000 with the X-Y movable reticle:


Meade_07068_9mm_Plossl_Eyepiece_w_124032

And have a couple of micrometer eyepieces for microscopes (with one marked handle).

By the way, in most cases, all you need to illuminate a non-lit reticle is getting some scattered light into your aperture (e.g. tape a piece of paper to the OTA rim and shine at it with the flashlight, the finger works too :) ).
In a light polluted sky it's not necessary at all as soon as you are well dark adapted.

 

Edited by AlexK
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39 minutes ago, AlexK said:

In a light polluted sky it's not necessary at all as soon as you are well dark adapted.

I was going to say as well, on most nights in my Bortle 5/6 skies, I can readily see the reticle against the background sky glow once dark adapted.

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18 hours ago, Neil H said:

Hi i use a telrad and cross hair eyepiece it works well together the eyepiece is only used for alginment 

Hi Neil, I have a Telrad that I find great for doing the two star alignment process and also for locating easy to find targets that don’t require use of the GOTO and therefore no two star alignment. I also use a flip mirror when imaging planets with my ZWO and for that of course I require an eyepiece, but the one I use isn’t ideal. The eyepiece is a 12.4 mm which gives a nice wide fov thereby making locating a planet very easy, but it can prove problematic getting it centred accurately enough to see it on screen, I need a reticle eyepiece, but don’t need it illuminated.

I am currently looking at a Meade Crosshair Optical Finder 8 x 21mm for £30 on eBay, it looks like it will be good for the job and at that price I can’t really go far wrong.

Ideally though I would like my 12.4 mm with a reticle because I like it’s wide fov and the large diameter eye lens.

Could you please advise me on the reticle eyepiece you are using and how satisfied you are with it.

Thanks.

Edited by Moonshed
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2 hours ago, Moonshed said:

I also use a flip mirror when imaging planets with my ZWO and for that of course I require an eyepiece, but the one I use isn’t ideal. The eyepiece is a 12.4 mm which gives a nice wide fov thereby making locating a planet very easy, but it can prove problematic getting it centred accurately enough to see it on screen, I need a reticle eyepiece, but don’t need it illuminated.

I think, I have mentioned the EP which would work best for your second stage pointing task above: "Meade Series 4000 illuminated reticle 9mm" (they might have 12.5mm like that as well, not sure, but the 9mm might be adequate for your 8" SCT already). It has a movable reticle which you calibrate first in meridian and to have its center pattern coincide with the camera chip FOV in the much wider EP FOV. Then just placing your target (planet) into that FOV marker circle/square, with the mirror down, you will always have the target centered on the chip with the mirror up.

Edited by AlexK
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6 hours ago, AlexK said:

I think, I have mentioned the EP which would work best for your second stage pointing task above: "Meade Series 4000 illuminated reticle 9mm" (they might have 12.5mm like that as well, not sure, but the 9mm might be adequate for your 8" SCT already). It has a movable reticle which you calibrate first in meridian and to have its center pattern coincide with the camera chip FOV in the much wider EP FOV. Then just placing your target (planet) into that FOV marker circle/square, with the mirror down, you will always have the target centered on the chip with the mirror up.

Many thanks for your recommendation of the Meade 4000 illuminated reticle 9mm. I can see that it is a good eyepiece that would perform well but to be honest with you it’s not really ideal for me. I do not need the eyepiece illuminated so I am paying for something I wouldn’t use and the other problem I have with it is the small diameter eye lens, I find it difficult to work with them, perhaps because I wear specs and have terrible astigmatism.
Regardless of that I do appreciate you taking the trouble to make a recommendation, so thank you for that.


 

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