Column Defects

[cardiofuse]

I have generated my PI Masters (Darks, Bias and Calibrated Flat).  The files look great.  When I Calibrate three Ha files, one of two of my column defects (seen on the Master Bias) is introduced into the image where no defects is seen on the Ha image.

Should I not calibrate with the Master Bias as some say that the Master Dark at the correct Time and Temp should already have the bias in the and should not be subtracted twice.

Looking for some guidance as I evaluate this software.

[jkmorse]

If you have your master dark at the same time and temp as your lights, you can just use the Dark without a bias frame.  If you do include the bias and the dark, you need to check the "optimize" button so that the Bias is removed from the Dark before calibrating the Lights.  Otherwise you will end up subtracting the bias twice and introduce the types of artifacts you are experiencing. 

As an aside, there are lots of places to look for help in getting started with PI.  Harry's Astroshed is a great place to start.  Also, I have a comprehensive cribsheet that I freely share.  If you are interested, just drop me a note at jkmorse57@gmail.com and I will be happy to send you a copy.

Best,

Jim

[cardiofuse]

Many thanks for the advice.  I did try to eliminate the Bias to avoid the "double subtraction you indicate".  Not sure why that didn't work.
I'll have to try it on another target. 

I did use CosmicCorrection to identify the two bad columns and it worked perfectly to average out the pixels.  Amazing and easy to do.

[jkmorse]

Curious what equipment you are using, specifically your CCD.  I have had a similar problem with my Apogee F16M (which has been a disappointment pretty much the whole time I have had it).  It used to be terrible horizontal lines that took a return to the factory to fix, now its vertical banding which at least I can manage. 

Jim

[cardiofuse]

Jim, I'm using mostly the ST-10XME due to the QE and it works well with my Tak TOA 150 on a AP900 mount.

I'm considering, after many years of upgrading and was looking at the STT8300 due to the two stage cooling, defrost and guider post filters, etc.  I'm worried about losing some QE during subs but not sure if it's significant. 

Actually, the two column defects on the ST-10XME haven't been a problem until recently for some strange reason.  I use a separate guide scope and PHD2 with MaximDL to acquire so no good way to dither unless I use the guide chip on the ST10.

I need a clear night to get another/different target to see if there's still an issue.  Say to remove during processing but still a mystery.

I've been having a problem with frost on my ST10 despite baking and replacing numerous packs of desiccant in my chamber.  It will sublimate off in about an hour so I have to turn the camera on early.   Might be a leaky chamber seal...

[jkmorse]

I am a big fan of the SBIG 8300's and in fact have two, an STF8300 and the STT8300 with the self guiding filter wheel and the AO8.  They take great images, much cleaner than my F16M.  That's why I am thinking about converting to an SBIG STXL6303E as my big CCD.  I have not seen any issues with QE on the 8300's and, when married to my Tak e130D can get great subs in just 2-3 minutes for RGBs and 4-5 with narrowband.

On the dithering front, any reason you don't use MaximDL's autoguiding routine?  I recently switched away from MaximDL to Software's Bisque's Camera Add-on since I run the full SkyX suite with my SB Paramounts, but I found the MaximDL autoguide routine easy to use and it gave excellent results.

Jim

[cardiofuse]

That's good to hear.  I'm getting close to getting an STT8300.  PHD can be placed in a server mode and with another piece of software talk to Maxim while guiding.  I've used Maxim guiding in the past with mixed results on accurate calibration.  I believe these issues have been addressed yet I am left with guiding behind NB and other filters which can make guiding spurious.  Then there is the "how lucky do I get" with selecting a guide star without camera rotation and then taking more flats.  I use an STi with an OAG on my AP130 scope and an OSC 8300 that works well for that setup.

[pfile]

i really like my STT. it's a great camera with rock-solid cooling. only thing is i've had to bake the dessicant a few times. when your flats have a border that looks like an 1950s tube television set bezel, you know it's time

rob

[cardiofuse]

I read that mid 2014 SBIG was having a problem with the AO8/STT configuration after some updates.

Are you using it for your sole guiding platform?

Not sure why I'm having frost issues, baked 3 times and been using a desiccant pack holder which should be very effective.

Thinking of putting the whole camera in the oven at 100 degrees.

[pfile]

yeah they seemed to be thrashing pretty hard on the driver/firmware and maybe even FPGA updates for a while there. to be honest maybe it is still going on - when DL bought SBIG they moved the support to the DL forums, and so no more announcements on the yahoo mailing list. i havent really been following the DL forums.

having said that, i updated everything a few weeks ago and so far so good. there is one bug that causes a downloaded frame to have a weird black and white stripe at the top, but that's been there forever, even when i was using the camera under macosx. i guess it must be a camera firmware bug. but it happens very infrequently.

because of the reducer spacing i need on one OTA, i sometimes use an external guidescope with a lodestar. but i've never been able to fully conquer differential flexure, so my preferred method is to use the self-guiding filter wheel. unfortunately the reducer spacing is clearly too far when using the FW8G but i'm kind of stuck...

rob

[jkmorse]

They have updated their drivers several times since and all seems fine, though I have only started to play with the AO8.  When I use the STT with my e130D there is no room in the image train re focusing.  There I use the internal guider.  I use the AO8 with my Planewave CDK12.5 and in my tests it produced very good results but it will really come into its own in around 18 months when I retire and get set up in a permanent observatory.  Then I can really zero in my polar alignment with my Paramount and between that and a 500 star TPoint calibration run I am planning so I can take advantage of The SkyX's ProTrack, I expect imaging nirvana. 

[cardiofuse]

The ideal system would allow the post filter pick off CCD to rotate independent of the camera angle.
I'm not sure if the new STT8300 does this. 

I have plenty of back focus with my TOA 150 and I spent the time to mount a Borg 60 on a rock solid dovetail plate.  So far guiding has been stellar beyond 30 min subs.

I was attracted to the AO8 for other atm, wind and vibrations.  No sense spending $795 for a paperweight.  I hope they get things resolved.

[pfile]

unless they have revamped the FW8G design, the pickoff prism is fixed (but it is in front of the filters, so there's that).

so you'd have to rotate the whole camera. i think the QSI works the same way.

rob

[jkmorse]

In my CDK image train I solve that with a Pyxis rotator.  Even though the the guide chip is fixed, I can rotate the FOV as necessary to pull in a good guide star, which is critical because, unlike my F16M which has a nice wide 50+ minute square FOV, with the STT its only 18 x 12 minutes.  Great for close in work, but guide stars are a challenge.