Guiding in narrowband with 2600MM Duo

Moontanner

Can anyone share their experiences while guiding in narrowband with the Duo cameras?

I'm interested in finding out how narrow I can go before reverting back to an OAG.
Please include scope type, F ratio, exposure time, gain setting, filter details, and anything else that might be useful.

I'm mainly shooting through a SW120ED Esprit with x0.77 reducer @ F 5.4 and I'm hoping I can use the Antlia 4.5nm Edge SHO filters.

Thanks.
Ross.

9kr69ubP

No problem @f4.9 using an Antlia Dual Band ALP-T. I did up the guide cam gain (250 from memory) to maintain a 1 sec guide exposure on my AM5. Plenty of heathy stars to use.

Moontanner

9kr69ubP Thanks for the info. 2x3nm @ 1seconds sounds promising. Or is it one of the 5nm versions?
The camera should arrive next week, so I guess I'll need to get my hands on a few filters to test things out myself.

Cue heavy clouds. They already stuffed up my attempt at capturing a timelapse of the aurora last night with the new ASIAIR Mini.

Eric

I've been using an ASI2600mc Air with SVBony 220 filters (both the h-alpha/Oiii and Sii/Oiii), which are 7nm/7nm filters, on a Sky Watcher Quattro 200p at f3.8. I found that to get lots of good guide stars I had to increase the gain to 400, with 3s guide exposures. I'm very surprised to hear someone using a 3nm or 5nm filter at gain 250 with 1 sec exposures at f4.9 and getting stars to guide on.

I'm planning on getting a 2600mm Air and moving the 2600mc Air to our 130mm refractor, I'm going to be using the optolong 6.5nm/7nm narrowband filters with the 2600mm Air on the Quattro 200p. I don't foresee any problems, hopefully it works just fine. I really wish ZWO would add a guide camera gain setting in the plan mode so when I switch from Lum filters to HSO filters I can have the plan lower/increase the gain accordingly to help with guide star acquisition.

Moontanner

Eric Thanks for the info, Eric.
Bring on the guide settings in the Plan feature! I also love the idea of the guide chip FOV showing up in the star atlas when selecting a target. Both would be great additions to the ASIAIR App.

It's safe to say that I won't be getting rid of my L-OAG just yet. My hope was to use the Duo guide chip to fit the CAA in place of the L-OAG, but I can live without the CAA if needed.

Moontanner

After going back through my notes, it would seem that using the 0.77x reducer is a no go. The image circle doesn't seem to be big enough @ 34mm.
I'll test it out once it arrives to see how bad the vignetting is. There's a chance the Duo chip might still be ok for LRGB guiding if I can widen the image train as much as possible?

Anyway, at the end of the day, using the standard flattener isn't the end of the world. The FOV with the standard flattener works well for most targets. If I want a wide FOV, it's really more appropriate to swap over to a different scope.

I'm still waiting on a response from ZWO support.
The joys of amateur astrophotography!

jKIoqOme

I have the 2600MC Air on my 800mm f4 ONTC Netwtonian + Paracorr 2CC + AM5N (so same guiding setup as the DUO) and frequently use the Optolong Ultimate 2" filter.
After a lot of testing with the Optolong Ultimate I achieved my best guiding at gain 600, Bin2, guide darks, 1.5 sec guide exposures. This results in an avg .5arcsec guiding all night long. Occasionally I have had to extend the guide exposure to 2secs depending on seeing and then guiding drops to .7arcsecs.
I have also used this setup with the Starizona Nexus .75X Coma correcter, and although the official specs say that the image circle is only 28mm, there is still enough light reaching the guide sensor to achieve sub .5arcsec guiding even with the Optolong Ultimate.