10 replies to this topic

[nsubin]

Hello all 

 

Still a bit of newbie. I've recently started to use an Antlia ALP-T Dualband 3nm Ha & OIII Filter with my ASI2600MC Air to try to image the Squid Nebula. Initially, after some challenges, I was able to get same adequate guiding, but I'm still getting a bunch of bad subs. Last night for example, I took 51, 300 second subs and when I ran WBPP this AM on them to see how I did, all but 9 were rejected. I know I keep losing my guide star. Is there anything I can do? I've changed to a 10 second exposure and pushed up the gain on the guide camera but still having this issue. I'd like to get much more integration on this target, I'm only about 9 hours in and I know that's not nearly enough. I'm frustrated, it feels like the filter is really diming the guide stars.

 

Thanks in advance 

 

Neil

 

 

[Tapio]

What is your guiding setup - scope/oag, guide camera?

What is your mount?

Oops, notice you had ASI2600MC Air with internal guider. That can be difficult with narrowband filters.

But the mount question remains.

Oh, and what is your imaging scope?

[nsubin]

Thanks for the reply Tapio

 

Scope - WO FLT 132

Mount -ZWO AM5

[Tapio]

Thanks for the reply Tapio

 

Scope - WO FLT 132

Mount -ZWO AM5

Well then, 10 second exposures are not going to work very well with that kind of SWG mount.

Don't know if it would be better to use a separate guidescope & camera.

[Brian Carter]

I have an AM5 and there's no way it would guide well with 10s exposures for guiding, these mounts just can't do that.

 

I don't know if the ASIAir has this feature, but there is a "Guiding Assistant" tool in PHD2 that I use.  It does a lot of stuff, but it provides two metrics that I look at:  First is the PA error, the other is the maximum guide camera exposure.  This will tell you roughly how long you can go without a guiding correction.  

 

I have never gotten this number >7seconds in my AM5, and this is after spending too much time doing drift alignment.  My usual PA provides me with 2-3 seconds, and I always keep my guiding exposures at 1sec.

 

All this to say, see if you can find something similar and really dial in your PA.  Then don't choose a guiding exposure greater than that number.  I recognize that this makes guiding narrowband really difficult.  Frankly, that is why I didn't buy that camera and went with a dedicated guide camera and OAG.

[Juno18]

The filter is absolutely dimming the guide stars.

I also have the Antlia ALP-T 3nm Ha & OIII filter (recent purchase) and I struggled with plate solving, PA (TPPA in N.I.N.A.), and autofocusing. I had to up the exposure time to 10 seconds (from 3 seconds).

Luckily, I am using an oag with the 220mm mini and guiding was not a problem.

 

I hate to think that going with a seperate guide scope/camera. 

 

Have you tried the ZWO User Forum? https://bbs.zwoastro.com/ 

Surely someone else is running a similar setup as you and might have some suggestions. Best of luck!

[KTAZ]

You are having the exact issue why many imagers just won't buy that camera. Both of my rigs have either a dedicated guide scope/cam or an OAG to ensure that the filters do not interfere with my guide stars. Sounds like longer exposures may be the only option. The ALP-T is my favorite filter, BTW.

 

Have you tried binning the guide camera 2x? Is that possible to do with that particular camera?

[PhilHoyle]

The specs I see on the flt132 say that it has a 32mm image circle. That's not big enough to illuminate the guide chip on the 2600mc air.

[PhilHoyle]

Correction 36mn, but still not big enough.

[nsubin]

Thanks all. Phil, would that imply that I'd have guiding issues even without the filter? 

 

I've decided to add an ASI120MM and a William Optics UniGuide 50mm Slide-Base Guide Scope (ordered from High Point yesterday)

 

Neil

[bdjeep]

I use my 2600MC air with Askar D1/D2 filters.  I think the bandpass is around 7nm, so that might make a significant difference.  I don't usually have a problem unless there is a lack of brighter stars near the target.  A slight reframing or rotating can sometimes help with that. 

 

I set the guide camera gain to 350 and use bin2.  I'd also recommend setting up a guiding darks library.  That helps with picking the stars out of the noise. I usually guide around 1-1.5s exposures with filters.

 

My scope is an AskarV.