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Old 03-05-2020, 10:22 AM
DRCORTEX (Lance)
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Telrad, Rigel, or Correct View Bintel finder

Hi All,

I have a CPC800 with Starsense, and I am looking at options to remove the standard Celstron 9X50 straight through finder.

I am considering either a Telrad, Rigel or right angle correct view finder.

Now the questions:

I understand the Telrad is larger/bulkier than the Rigel, which would add weight, on the other hand the Rigel is taller.

Which would suit the CPC800 ?

The Rigel, seems to be around the same height, as the starsense in refernce to the OTA. Would I need risers with the Telrad to do the same ?

Really, I wouldn't be using them for star hopping, but simple calibration of the starsense, and verification of that calibration. Once calibrated, I switch to CPWI, and Toupsky for video astronomy.

I have also thought the Bintel right angle correct view 8X50 finder may be an option. It certainly would save me bending, and wow, my back is not good.

Your thoughts ?

Cheers

Lance
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Old 03-05-2020, 10:24 AM
jamespierce (James)
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A telrad and a rigel will both do the job. We have have a mix of both on our scopes. I would suggest that a Telrad is a little easier to use, the extra 4 degree field can be helpful if matching to charts and star hopping.



Both need to be aligned pretty much every time. The rigel uses a shorter lasting, harder to find battery.


As long as you can sight along it the Telrad will not need a riser.



TLDR; Rigel for small scopes, Telrad for everything else. You probably want a Telrad.
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Old 03-05-2020, 10:42 AM
astro744
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A Telrad and RACI finder is the best combination. One points you to the sky and the other then shows some fainter field stars within the Telrad 4 deg field.

I use a Telrad and 80mm RACI finder with an eyepiece that gives a 4 deg field riding on my C9.25. My beefed up GM-8 (CG-9 1/4”) handles it just fine. I have Telrads on all my ‘scopes and I will invest in the Stellarvue F50 or F60 RACI finder one day to put on my Dob. The F80 although light still makes the Dob a bit top heavy.
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Old 03-05-2020, 12:12 PM
raymo
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Hi Lance, if it makes your decision any easier, I have an Orion 9x50 RACI
finder as new, you can have for $75 posted, an extra $10 if you need the dovetail base. PM me if interested. I hope I'm not breaking any forum rules by making this offer.
raymo
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Old 03-05-2020, 12:36 PM
rrussell1962
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I have a Nexstar 8SE with a Starsense. Unless you remove the Starsense you only need to do the calibration once and you do it through the eyepiece at high power. I would go with the cheapest possible option if you are convinced you need to replace the Celestron finder. I used a cheap red dot finder and now the Nexstar puts objects in the field using an LVW 17mm eyepiece and I have not tweaked the backlash yet.
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Old 03-05-2020, 02:03 PM
Renato1 (Renato)
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I have great difficulty finding a bright star with a straight through finder using one eye open and one shut like when shooting a rifle. But it is much easier when one keeps both eyes open.

If all you want is bright stars for calibration - try that first.

If it's still annoying, while a Telrad is the best, cheap little red dot finders are plentiful on Ebay. They weigh little. Just find a screw somewhere on your telescope, take it out, screw part of the red dot finder base down into that screw hole, and use a piece of double sided mounting tape on the other side.

On some of my telescopes, I've screwed down the actual mounting base that the red dot finder slides into. On others, I've used red dot finders with a curved base with screw holes.

Then its a case of red dot finder on the star, look into straight through finder and centre it exactly.
Cheers,
Renato
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Old 03-05-2020, 04:56 PM
DRCORTEX (Lance)
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Hi Raymo,

The dovetail plate, what is the distance between the screw holes. I have had a tonne of problems with the standard Celestron one. To attach a finder and the starsense to the CPC800, you actually need to turn one around or it won't go past the fork. Even then, the finder won't fit properly, hence another reason to look for different options.

Cheers,

Lance
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Old 03-05-2020, 05:06 PM
DRCORTEX (Lance)
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Thanks everyone for your input.

I think I might try for the best of both worlds. Why settle on just a finder, when perhaps I can find something that will serve as both a finer, preferably RACI, and double as a guide scope down the track if the right angle recticle can be unscrewed.

I may be able to use my GSTAR-EX3 as a guide camera in that case. The Telrad seems to be the right option, simply for that initial lineup.

Someone suggested, the Starsense never needs calibration again, but with my bumping, and dragging the mount around, it invariable does need realignment to some degree. Have had some problems with it lately, keeps telling me I am +/- 10 degrees out so fails calibration. Might do a factory reboot when I get time. I've been using Alpha Centauri for calibration, and knowing my stupidly, I am probably lining up on Hadar

Cheers,

Lance
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  #9  
Old 03-05-2020, 05:35 PM
astro744
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Stellarvue will give you the finder and guidescope option you desire.

See https://www.stellarvue.com/f50/

Get the F50 RACI finder and non rotating helical focuser and your set.

'and' get a Telrad not 'or' and your set as they complement each other.

Note you need to get rings and a mounting foot/base for any Stellarvue finder. Note too the Stellarvue eyepiece can be replaced with any 1.25" eyepiece. I typically use a 19mm Panoptic or 16mm Nagler on my F80M for a slightly higher power and still get 4 deg. highly corrected field. The finder is f3.75 so it's tough on wide field eyepieces unless the eyepieces are highly corrected themselves. Typically this is not a concern for a standard finder eyepiece. The 23mm eyepiece supplied by Stellarvue works fine and the cross hair can be illuminated if you desire. I prefer no illumination and don't miss the cross hair when using the Panoptic or Nagler.
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Old 03-05-2020, 06:14 PM
raymo
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Hi Lance, the distance between hole centres is 21mm.
cheers raymo
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  #11  
Old 03-05-2020, 07:48 PM
DRCORTEX (Lance)
Neo - as in Dr Neo Cortex

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Sorry, won't work, screw spacing is 35 or 45 mm. I really don't think that Celestron put much thought into "standardizing" mount options, just like any car manufacturer.

They all say, will fit most telescopes, but your own, invariably, is the least.

Cheers,

Lance
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Old 03-05-2020, 07:57 PM
DRCORTEX (Lance)
Neo - as in Dr Neo Cortex

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Thanks for that re the Stellavue - might give Bintel a ring, see what they suggest.

Cheers,

Lance
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  #13  
Old 04-05-2020, 07:53 AM
rrussell1962
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Hi Lance, just re your calibration issue. In your post number 7 do you mean that you reversed the Starsense bracket for the CPC as per page 10 of the manual? If so, you didn't accidentally unscrew the Starsense lens when you took off the lens hood to reverse the bracket?
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