andrew s

@vlaiv are these differences to be expected? Maybe a students t test would tell you if they are. Regards Andrew

The reason I would not use scaled darks is because of amp glow. This adds additional signal and has shown to be non linear. The reasons I don't think gain change is likely are two fold; Firstly, the big advantage of CCD and CMOS is their linear response to light so to deliberately subvert this with a time dependent gain would be perverse (although it might be unintended). Secondly, where careful study of the ASI 1600 has been done its response was measured to be linear. This would normally be done with a constant light source and increasing the exposure. If gain changed with time the result would be non linear. Have a look at these two studies by Christian Buil who is a well respected for his work in this area and the premier amateur spectroscopist. http://www.astrosurf.com/buil/CMOSvsCCD/index.html and http://www.astrosurf.com/buil/atik_vs_zwo/ From my own experience of measuring the ASI 1600 MM it behaves very well and as I expect. I suspect based on issues I have had in the past that taking multiple short exposure lights, barks or bias frames without any delay between them can give erroneous data. I always input a delay to ensure (as far as possible) that each frame is taken under similar conditions. Regards Andrew

This seems very unlikely to me. Can you provide a reference to support this that has any evidence rather than anecdote. Thanks Andrew

Looks like a very good first go. I would advise rotating the grating to align the spectrum with the camera rows as software rotation adds artifacts and reduces resolution. You look to have got good focus which is often difficult. The calibration looks fine. The O2 is teluric in origin I.e from or atmosphere. The Fe and Mg may not be real. I would need to check. Great start. Regards Andrew

With a CMOS camera I would advise using the same gain for flats and lights. Changing the gain may impact the individual A to D and amplifiers differently which would invalidate the flats. I also insert an exposure delay in taking Flats and Darks ( and Bias with CCDs) to ensure the camera has stabilised between readouts. It is best to be over cautious incase there are hidden effects. Regards Andrew

These are not hot pixels but warm. They do seem to calibrate out. The term was mine I would call 10,000 a storm 😀 Regards Andrew

I found this Sony chip had a temperature dependent snow of warm pixels. See here for a discussion http://www.spectro-aras.com/forum/viewtopic.php?f=8&t=1919 Regards Andrew

Doing the calculation first would have saved you the effort but at the price of the fun in trying it 😀. Regards Andrew

If the bias were unstable then so would match darks and flat darks as they include a bias component. In fact it would be unusable. When I measured my ZWO ASI 16000 M the bias was perfectly stable across time and switching on and off. The only reason to not use scaled darks is due to the nonlinear amp glow. Regards Andrew

Very good image as is the NGC772 but both would benefit from double the image scale (and resoution) in my opinion. Regards Andrew

I came across Pixel Skies via Ian King Imaging. I had inquired about hosing at the IC Astronomy site at Oria in Spain but it was full. However, a new site was under development at Castillejar which was owned by Pixel Skies. On the ground both are manged by the same quartet of people. I decided to take my kit to Castillejar and was met at the Petrol station by Dave and Colin who led me out of the village to the site. On approaching the site I was struck both by the security fencing and how spotless the area was. The equipment was quickly unpacked with the additional help of Michelle and Sam who also offered refreshment. The observatories are of a run off roof design but the mount and telescope are installed so as to allow the roof to close whatever the position there are in. The intended pillar for my set up was too tall so a visit to Oria was required to fashioned a new pillar. This allowed me to see that site which is very similar to the one at Castillejar, It too was spotless inside and out and housed an impressive array of both commercially owned and private equipment. Unfortunately, that prevented us from setting up that night but that was compensated for by just seeing such a magnificent sky. The Milky Way was overhead and I could trace the ribbon easily. I could see no trace of light pollution. I was staying at the site on a B&B basis. The accommodation was in a cave house common in the area and was spacious and furnished to a very high standard and a well stocked fridge to provide breakfast. Next day, the equipment was installed by Colin and Dave. I was impressed by their working practices which kept the area clean with no dust. They clean the equipment regularly the scope already in the observatory I was sharing was spotless. I was allowed to fit my spectroscopic back end and gps clock etc. Again all was kept neat and tidy. While I had an IP Power switch they can be provided as was a UPS. Dave also installed their preferred remote access software and the roof control and monitoring software on my PC. One of the benefits at Pixel Skies is that they manage the opening and closing of the roof and being on site if problems arise. The also have a problem reporting and ticket management system shared with IC Astronomy, although I have not needed this yet. That evening I polar aligned and did a 255 point Tpoint model only 3 point failed to image link and all the rest were accepted in the model which gave ~16 arc seconds pointing better than I got a home. One consequence of the roof missing the telescope is that it restricts the horizon to about 30 to 40 deg in my case. A small price to pay in my view. On my final night I check the alignment of the spectroscope and took some test data. The next morning we signed the contract and said farewell after a delightful visit. Security is good at the site, with fence and metal doors with bar and lock. It is remote and manned most of the time. For anyone considering a full hosting option or just needing a pad to set up an observatory I have no reservations whatsoever in recommending Pixel Skies. They have a web site here https://www.pixelskiesastro.com/ or can be contacted on info@pixelskiesastro.com. Regards Andrew

I made a ramp that bolted to the vesta plate and slid it up with the help of a friend. With the counter weighs on and the mount with weights down vesta plate pointing at Polaris. Regards Andrew

Enjoy, my ODK 16 is a two man lift. Regards Andrew

I always keep the PC on. Regards Andrew

You can put shims under one or other of the tube rings to reduce cone error. Bit trial and error to work out which way to go. I have done this in the distant past. Regards Andrew

Very nice looks like the Milkyway is coming from the chimney. Regards Andrew

I would just add weight either roofing lead cut to size or small exercises weights that fit on a bar. Attach to the underside of the dovetail plate if you can. Don't forget to rebalance in RA. Regards Andrew

The bands below 6850 are due to oxygen molecules in the earth's atmosphere. Regards Andrew

Just to round this off I got back safe and sound following a 200 mile detour to avoid road blocks on the AP-7 in Spain and an encounter with the French customs who pulled me over on the motorway to search the car. It seems too many of us geriatrics are supplementing their pensions by being drug mules. I am now working through all the necessary steps to characterize and calibrate the new spectroscope but here is a raw spectrum from a calibrated image of 61 Cyg taken remotely at Castillejar. The 61 Cyg A B pair are K5e and K7e here I have jogged the spectra to overlap. Sorry Olly I had already left by the time you posted. Regards Andrew

Have a look at the wikipedia article "Joule-Thompson effect" Regards Andrew

They don't have to be wild. In the distant past I was out using an eyepiece when one of my Burmese cats lept onto my back clinging on for dear life. That was a shock. Regards Andrew

"It's full of stars." Great start. Regards Andrew

Heading back tomorrow. He is a snap shot of Vega (0.01 s) taken from the Pixel Skies site. I will do a review of my experience here when I get back but it has been very positive. Regards Andrew

Maybe one way to look at this is via extreme. If the focal ratio is effectively 0 then all light goes to one pixel. Max SNR min resolution. Extremely large focal ratio minimum SNR max resolution. Same diameter scope. Regards Andrew

The only additional point I can make is the some use peak to peak values and others an average e.g. rms. Averages ,look better that p to p for the sa e optic. Regards Andrew