A couple of galaxies

[JamesF]

A couple more images from the Photoline 72 and ASI174MM last night.  No filters, as for the earlier image of the Iris.  M51 is 30 minutes of 90s subs, stacked, stretched and cropped, but no darks.  Looking at the full frame it's quite clear darks are required, but actually I'm not unhappy with it.  It's also clear that this one needs a fair bit more focal length.  The Triangulum is also 30 minutes, but 300s subs this time, and includes darks.  Needs greater sub length I think.

 

James

Edited August 26, 2019 by JamesF

[rl]

excellent work

[wimvb]

Excellent. The 174 is a nice little camera, isn't it? With its large pixels, it works best at longer fl. It's still above 1"pp at 1000 mm. What gain did you use? 

[JamesF]

Gain was whatever is the default in INDI.  The only camera setting I changed was to use 16 bits rather than 8.

James

[wimvb]

54 minutes ago, JamesF said:

Gain was whatever is the default in INDI. 

0, I believe. In that case, 300 s exposure as you wrote in another thread, is about the longest practical. I've more or less settled on 120 s at gain 20 for L, and 240 s for rgb. 

[JamesF]

300s seems to be the maximum for the 174MM.  Not sure why.  Perhaps ZWO felt that was the maximum it could stand without cooling.  The Altair camera based on the same sensor can go up to 1000s I think.

James

[wimvb]

Mine is the cooled version. I wasn't aware the uncooled version has this short exposure time limit. 

[JamesF]

Ah, that really does make it look as though ZWO decided it wasn't good for longer exposures without the cooling.

James

[wimvb]

The 174MM-Cool has been discontinued. What does that tell you? 😉