best camera for all sky use

[Horwig]

What, no Gina in shot?

[Gina]

I was hoping to see what the hot pixel situation was like with long exposures but the only program that I have that will do 60s exposures with the QHY5L-II-C is Sharpcap and that seems to have stopped working   oacapture has the 10000-100000ms range for the QHY5 but not for the QHY5L-II-C   With the new camera the maximum exposure is 10s.

[JamesF]

I'll raise the limit for that in the next release

James

[Gina]

What, no Gina in shot?

OK - Try this one

[Gina]

I'll raise the limit for that in the next release

James

Thank you James

[Horwig]

EZPlanetary's long exposure mode control is under 'camera setup / advanced settings' . Then goes up to 1000 seconds.

also a setting here for delay between frames, but no description of what the numbers mean,.

The lens has a backfocus of 7.82mm according to the fuji usa site: http://www.fujifilmusa.com/products/optical_devices/security/fish-eye/vari-focal/yv22x14a-2/

The camera is 10.4 according to this: http://www.365astronomy.com/images/D/QHY-5L-II-planetary-guide-cmos-camera-sizes.jpg

Huw

Hang on, I've just considered what I posted. According to these figures, the lens will not make focus, someone's figures are wrong!

H

[Gina]

The discrepancy I'm finding is about 1mm whereas the difference in those figures is 2.58mm.  I think I should be able to get away with a spacer which I'll try printing out of ABS plastic.

[Horwig]

Yes, the difference might be 2.58mm, but it's in the wrong direction according to those figures, the camera is deeper than the lens backfocus.

Incidentally, the backfocus for a real CS mount should be 12.526mm

H

[Gina]

Back to EZPlanetary...  Found how to set long exposures now   Here's a 60s exposure with the shutter closed.  Certainly could do with cooling for stargazing   I'll see what I can do.  It might be a case of buying another lens and using the cooled QHY5 for the stars and QHY5L-II-C for daytime.  I'll try the latter with the night sky first though.  If, as I suspect, the QHY5L-II-C is more sensitive than the QHY5 I might be able to get away with a lot less exposure time.

[Gina]

Yes, the difference might be 2.58mm, but it's in the wrong direction according to those figures, the camera is deeper than the lens backfocus.

Incidentally, the backfocus for a real CS mount should be 12.526mm

H

Oh yes, so it is!  Very odd...

[Gina]

I've printed a spacer to get focus - turned out to be 1.2mm rather than my estimate of 1mm   I can now focus with the focus lever for fine focus   Image is very slightly higher than the frame with minimum zoom but not too bed.

[Gina]

Been thinking about cooling.  Cooling the case is none too easy being round so I might take the sensor PCB out of the case and see about directly cooling the back of the sensor with a small Peltier TEC.  The board is held in with two small Philips head screws into threaded holes in the case.

Weather forecast for tonight is clear sky so I think I'll lash up a mounting and see how my QHY5L-II-C does with the stars.  ie. see how bad the background noise actually is and what exposure I shall want.  I would like to use the same camera for day and night to save buying another fish-eye lens at over a ton

[Horwig]

I've played with dark subtraction in EZPlanetary, very easy, exposures of between 10 and 30 seconds work for me.

Huw

[Gina]

Good   Thank you

I've had the sensor PCB out and there's a pad directly on the back of the sensor going through a hole in the PCB and this engages with a post on the partition - clearly to conduct heat from the sensor to the case.  There is also a pad on a chip (presumably the imaging processing chip) which also contacts the partition.  So it seems they have thought about cooling and probably done the best possible apart from including active cooling

I've no doubt I could arrange to cool the case with copper sheet wrapped round it with thermal grease in between - I still have some of the super-conductive thermal grease left.  Then that could be thermally attached to the cold side of a Peltier TEC.  But from what you say it may not be wanted and I'm not looking for extra work - I have plenty already

If anyone felt so inclined an alternative would be a small Peltier TEC on the other side of the partition with the other circuitry taken outside.  See my earlier photos.

Here's what the insides look like.

[Gina]

I've designed and printed a bracket to hold the camera plus lens on the end of an aluminium tube attached to the south side of the bungalow.  The ASC is about 2ft above the edge of the roof.  The tiles and chimneys can be seen in the image capture attached.  I didn't get the angle right and the brick chimney is roughly north.  I'll see if I can put this right for tonight.

[Gina]

Brought ASC back in but before doing anything else, here's a view through the open window.  With the spacer between lens and camera I can focus the image well with the focus lever on the lens.  Really accurate focus with the aperture wide open at night will need the stepper motor drive but manual works well enough with the aperture set for daylight   I've brought the ASC in because I'm looking at saving a dark frame next.

[Gina]

I'm gradually getting the hang of EZPlanetary - it's good   Captured 10 dark frames of 20s ready to use tonight   Also, found how to get the other end of the exposure range and running with an exposure of 120us in the screenshot attached.  With this low exposure I can open the aperture fully in daylight without whiteout   This means I can use this camera for all day and night by just changing the exposure, so won't need the aperture motorised

[Horwig]

An aperture remote might be useful for darks.

Incidentaly, my system has a nasty habit of freezing, and I have to disconnect and re connect the camera to bring it back.

Huw

[Gina]

Ah yes, you're right Huw, I'd forgotten I use remote aperture for darks.  Anyway, the aperture is quite easily motorised

EZP hasn't stopped on it's own yet but I used to get that problem with SharpCap.

[Gina]

Here are some photos of my test rig.  (I can see more property repairs I need to do too )

[Gina]

Sunsets should be nice with this camera

[Gina]

Supposed to be completely clear sky by now - huh...  Wonder if the clouds will go away.

[Gina]

 Well, the clouds have nearly all dispersed but the moon is rising and it's pretty much full.  Stars are starting to show

[Gina]

One from last night.

Light cloud with some sunshine this morning and even at minimum settings the camera is saturating in the very bright areas.  See attached screenshot below.  This indicates that aperture control will be helpful as well as for taking darks.

[Gina]

QHY5L-II-C  Results.

Assessment :-

Over all, I am happy to report that this camera is pretty good for all sky use with both day and night capabilities.  I wasn't able to get the best of the stars last night due to the moon and dew forming on the lens.  The former a well known problem with AP but the second is easily fixed with a heated dome cover and casing.  Dark noise seems pretty low even at 20s exposure with the camera casing simply air cooled.  I get occasional partial hot horizontal lines so camera isn't perfect (but few things are).

I think that now pretty much covers my assessment of this camera and details of the All Sky Camera I shall be building using it is a subject for a separate thread.

Conclusion :-

I am very pleased with this camera and when bought from Bern at Modern Astronomy via ebay, represents excellent value for money.