StuartT

Can I just check my calculation of the distance of this galaxy? I understand that the distance of a galaxy (which is outside the local group) is d = cz/H where d is the distance in Mpc; c is the speed of light in km/s; z is the redshift and H is the Hubble constant (70 km/s) According to Simbad UGC4526 has a redshift of 0.0147 so I make the distance to be 0.063 Mpc (or about 205 million light years)

Ok. I should prob learn how to do that. Do you know of any videos showing how it's done?

Ok, I’ve not tried that (I just use all the default settings in APP as I don’t understand what it’s doing anyway! 🤣) so could you assign the Ha and O III to blue and yellow to get something like a Hubble image?

Lovely image. Well done but I’m puzzled as to the colours. I shot the Rosette last night also with the L extreme and a colour camera, but mine is mostly red (presumably H alpha). so how did you get your colours?

Thank you. I never use exposures longer than 35 sec (as I have never ventured into guiding). With a camera as good as the 2600 and a target as bright as this, I’m not sure there is any need for longer exposures, frankly. But I’m happy to be persuaded otherwise.

Very nice! I assume that when you say ‘processed as Ha and O III you’re meaning some kind of pseudo-narrowband emulation using pixinsight from an OSC (rather than using a mini camera)?

Reasonably happy with this for only one hour of data. It's clearly a v bright target. Esprit 150 ED APO (with 0.77x reducer), ASI2600MC Pro, Optolong L-Extreme. 1.5 arcsec/px

ah, so it's actually pixel scale ratio (rather than FL ratio) that counts then? That's useful to know. Thanks. I plan to use a Meade LPI-G mono camera (which actually has the same pixel size as my main imaging camera - which makes life easier). So I should prob go for a guide scope with FL of 300mm then (for both my main scope FLs) Thanks so much

Esprit 150 ED APO. At full FL it is 1050mm and with the reducer it is 808mm

thank you. V helpful. What guide scope would you recommend? Is there a relationship btw the FL of the imaging scope and the guidescope?

I currently don't do any guiding at all. I wanted to master the basics first, so I have been keeping my exposures to < 30sec. However, I think it might be beneficial to think about guiding, as - even with an excellent camera - 30 sec may be too short for some targets. My question is, at what FL does differential flexure make OAG a necessity? My main imaging scope is FL=1080mm (or 808mm with reducer). Would it be necessary to use OAG? Or is that more for FL towards 2000mm plus? Thanks

Interesting. Thanks. I have ASTAP (it's my blind solver in NINA), but I've never tried stacking with it. I always use APP or Siril

well... this is what I got after over 3h of data. Not too impressive! But it's only 50 arcsec wide I guess. Galaxies are hard!

Ok, it's solved it, but it hasn't identified the galaxy

I'm going to image this galaxy tonight. Though it will still be fairly small in my Esprit 150

thanks. Uploaded it, but it's taking quite a while (about 15 min so far). Is that usual?

Bingo! That's it. Thanks. (I don't know my way around the apps, but presumably there is a way to search databases by RA and Dec?)

Last night I was imaging the Beehive Cluster and I seem to have got a galaxy too. But I can't find it in any of my atlases. Anyone know what it is?

thanks @vlaiv for this thorough explanation. I really appreciate your help. So I think I will probably go for the Quark combo then, for greater flexibility.

Right, I take the points about the need for higher frame rates. I can get away with imaging the moon with my OSC, but that is much less dynamic a target, as you say. Also, I understand that mono is better for the sun in any case. Thanks. I shall look into mono cameras with larger pixels and high frame rates (though I suspect options are very limited with these three requirements!) The one thing I still don't really understand (sorry to be dumb) is why there is a constraint on f-ratio for the Quark. How does the Quark 'know' what f-ratio rays it's receiving? Why does this matter? I assume then that the telecentric barlow (powermate or whatever) needs to be 'before' the Quark combo in the optical train?

Thanks so much for taking the time to explain all this @vlaiv I do actually have a larger sensor (the 2600MC Pro has APS-C sensor), but the frame rate is not so good as the Player One camera. Also I read that binning is best done in post processing, not at acquisition.

err... not really. There are a few things I don't understand there! So I think basically you are saying I can't have my cake and eat it. So I should probably just image partial disk (with a regular Quark) in high quality, rather than try and do everything

thanks again. I am not sure I understand how stopping down the aperture would change the size of the image. I though this just limited the amount of light coming through? For example, when I change the aperture on a camera lens, the image size doesn't change, just the brightness

So a couple of additional questions, if I choose to go with the Quark Combo 1) I currently have the Televue 2x and 3x Barlows, but it sounds like these would not be suitable? 2) I was planning on using the Apollo M mini camera, but this has a sensor height of 6.6mm. Would that only allow me a partial disk view? (I do have a ASI2600MC Pro which is a APS-C size, but it only has a low frame rate, so I am guessing this is not ideal for solar) What I would like to be able to do (ideally) is to have the choice of imaging both the full disk and close up views

Thanks @vlaiv this is really helpful!