f ratio for guidescopes

[dan_19991]

On 1/22/2018 at 11:05, Stub Mandrel said:

This is what happens if the stars all disappear behind cloud, PHD stretches the starless image (and the noise appears).

see thats what i thought but i was outside at the time and it was perfectly clear, it was only the one frame aswell and then it would go back to fine, it may have been it hadnt had time to acclimatize to the temperature outside but my dslr never does anything like it, i shall have another go tomorrow if the sky permits and report back. 

[Thalestris24]

35 minutes ago, dan_19991 said:

see thats what i thought but i was outside at the time and it was perfectly clear, it was only the one frame aswell and then it would go back to fine, it may have been it hadnt had time to acclimatize to the temperature outside but my dslr never does anything like it, i shall have another go tomorrow if the sky permits and report back. 

I guess with the long focal length it doesn't take much to fill the small fov with a bit of cloud. I think the camera can see a lot better than a person in that respect! I believe a typical 50mm guide scope would be much more tolerant

Louise

[Tommohawk]

On 1/12/2018 at 19:12, dan_19991 said:

thanks, that makes sense, and im afraid i have little to no backfoucus, im going to barely get a coma corrector in there 

Just a thought. TS Optics do an OAG for EOS cameras which is only 9mm "thick". Not cheap though! On the SW200P you could probably adjust the primary and shove it down the tube a bit to give you the back focus you need.

[emyliano2000]

On 24/01/2018 at 20:57, Tommohawk said:

Just a thought. TS Optics do an OAG for EOS cameras which is only 9mm "thick". Not cheap though! On the SW200P you could probably adjust the primary and shove it down the tube a bit to give you the back focus you need.

I have the TS09OAG for EOS and used it with my 200p, my 700D and a baader mpcc and I didn't have to alter the telescope at all. I could get the guide camera into focus but only at the far end of the prism. I got a 10mm extension tube that allows me to push the guide cam down a bit for a good focus and a good stability. The reason I switched to the 9x50 finder-guider is  that I was finding it hard to find a guide star for certain targets. 2x2 binning helped a bit. I wanna start using it again though because of the differential flexure.

Im using a Lacerta standalone autoguider if it makes any difference with the specifications in the screenshot below.