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Old 26-08-2020, 08:30 PM
Cyberman (Rob)
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Oag

Hi, Can someone please give me some advice re guiding. I have an EQ6R, skywatcher 250 F4 and Canon 600D. I was looking at getting an off axis guider to reduce weight. Any suggestions of which OAG equipment that is suitable would be appreciated, thanks, Rob.
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Old 26-08-2020, 09:05 PM
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muletopia (Chris)
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I used an Orion thin of axis guider with a Canon EOS 60Da and a ZWO ASI 120mm as the guide camera for some time. It worked well, it certainly lead to good tracking. This at a focal length of 2415 mm., PHD2 total guiding rms typically between .3 and .5 arc seconds with reasonable seeing, .7 to 1.0 on poor nights.


The downside is that it is sometimes difficult to find a suitable guide star.


Chris
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Old 27-08-2020, 06:40 AM
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doppler (Rick)
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+1 for the Orion thin oag. It's a big improvement in guiding rms over a guide scope. The trick with these is to to use thin spacers to get both cameras to focus while keeping the adjuster on the oag stalk in tight. I have mine on a 10" f4.7 newt , canon 1100d and zwo 120mm guide camera.
Rick
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Old 30-08-2020, 12:10 PM
gb44 (Glenn)
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Oag

Coma makes finding guide stars difficult too.

What about the On axis guider?

GlennB
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Old 31-08-2020, 12:19 PM
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Sunfish (Ray)
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I use an off axis guider on a F5 8 inch newt. Works fine even though the stars are a elongated. Plenty of stars as long as there is no obstruction near the edge of any kind.
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Old 31-08-2020, 08:15 PM
etill (Elliot)
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Depending on the backfocus you have it may be a tight fit to get an OAG in.

I have an F4 reflector and with the focuser on it there's no way I could get an OAG in with a DSLR, but it's fine with a QHY10 as there is more space between the sensor and coma corrector.

The coma doesn't cause me any issues for guiding, phd2 finds the centroid so the shape of the guide star doesn't matter that much. It is harder to find a star as reliably though, there are fewer of them and they appear to be fainter generally. I haven't run into issues with it more than once or twice. I have a zwo oag with asi120mini guide camera.

I think it'll probably come down to whether you have a coma corrector and the spacing required between it and the sensor. With a canon and something popular like a baader MPCC there's no room for an OAG.
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Old 06-09-2020, 02:34 PM
Cyberman (Rob)
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Thanks Elliott, Ray, Glenn, Doppler and Chris for your info. Looks like I will try the thin OAG from Orion. I saw there was a couple of TS OAGs . One was a 9mm and one attached directly to a DSLR. Has any one tried these. Also any suggestions for a coma corrector for sky watcher 250 F4 reflector. Cheers,Rob.
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Old 06-09-2020, 03:29 PM
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Sunfish (Ray)
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I have not purchased a coma corrector, but have looked at the models which provide 100mm backfocus . That would offer a lot of versatility and allow a DSLR and OAG.
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Old 06-09-2020, 08:16 PM
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doppler (Rick)
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Hi Rob, here's a link to an older thread.

http://www.iceinspace.com.au/forum/s...d.php?t=173966

A lot of people use the baader MPCC, but Skywatcher make a corrector specifically for their f4 scopes that's supposed to be quite good as well.
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Old 07-09-2020, 12:45 PM
porthacking (Scott)
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Hi All,

I too am looking at OAG for a RedCat/SpaceCat 51 (with an SWO guide camera). Apparently the Lumicon 2" easy guider (SWO version) is good. Does anybody know of any other options?

Thanks for your help,

Scott
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Old 07-09-2020, 01:52 PM
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Merlin66 (Ken)
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Scott,
An OAG would not be a good fit/ solution on the RedCat 51.
As an f5 with only 250mm focal length it, in itself would make a good guide telescope.
I assume you want to image with it. What camera/ mount do you have?
A small finder/guider attached to the RedCat would be a better solution.
Something like this:
https://astronomy-imaging-camera.com...inguider-scope
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Old 10-09-2020, 10:18 AM
porthacking (Scott)
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Hi Merlin,

Ultimately, I would also like a visual finder scope and for this I will need OAG because there is not room for both a visual finder and guide scope. I will be using a compatible ZWO camera. I have seen a few reviews that say it works nicely so was interested if anybody knew about other OAG options. That being said, I have also ordered a guide scope.

Thanks,

Scott
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Old 10-09-2020, 10:46 AM
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Merlin66 (Ken)
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Scott,
Don't know if it's of interest, but I used to have a 60mm finder set up with a flip mirror. That way it could be used visually and then flipped to allow imaging......
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Old 13-09-2020, 02:00 PM
porthacking (Scott)
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Hi Ken,

That's really interesting. A 60mm finder for my 50mm primary obviously would be amusing, but I'll keep this in mind for when I upgrade. What finder do you use?

Thanks,

Scott
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Old 13-09-2020, 02:28 PM
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Merlin66 (Ken)
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Scott,
Nowadays I only do spectroscopy and solar observing.
With the spectroscope fitted, the in-built "on axis guider" - a reflective slit plate is not suitable for imaging or plate solving.


I use a "generic" 60/230mm finder (similar to this: https://www.tomtop.com/p-e5765.html?...d=guscauylynew)
fitted with an old DMK51 camera which gives me 79 x 105 arcmin FOV.
I can usually place the target on the 20 micron slit gap, and if it's a difficult field, use the Astroart plate solving to nail the target.
HTH
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