Thalestris24

From jdupton on CN: " The reason I suggest cooling to at least around 15 degrees below ambient is to operate the TEC in an easily controlled zone in order to attain temperature stability. When the TEC is operating at less than about 5% of its power level capability, the stability of the sensor temperature will usually be less controlled compared to when the TEC is operating at about 30% power level. Conversely, then the TEC is operating above 80% power, self heating of the sensor by the camera body can start to affect temperature stability. I have recently run tests of this on my ASI294MC camera. I found that as the TEC approached 90% to 100% of power, the actual temperature of the sensor started rising due to excess heat from the TEC being dumped into the body of the camera. That in turn, raised the temperature of the sensor and reduced the stability of the temperature since the TEC is cooling the back of the sensor and the circuit boards to which the sensor is attached are warming the sensor. In my camera, this leads to an instability of the actual sensor temperature over the period of an imaging session.*

I may analyse the spectra I've already got but I probably won't do any more so won't be getting addicted! Louise

Still a lot of money! At least, for a poor person like me.

My SA100 is too deep to fit in a TS filter drawer and be able to slide the drawer in and out. Maybe something could be modified somehow...

They are over £3k! Louise

I just read your posts on CN and see you bought it second hand. Reiterating the relevant specs: Cooling: Regulated Two Stage TECDelta T: 35°C-40°C below ambientCooler Power consumption: 12V at 3A MaxWorking Temperature: -5°C—45°CStorage Temperature: -20°C—60°CWorking Relative Humidity: 20%—80%Storage Relative Humidity: 20%—95% You may be using the camera within spec but things can age and deteriorate. Under those circumstances you need to contact ASI and see about getting it serviced if it won't cool down to a delta of 35 deg. Only the surface of the TEC in contact with the sensor should get cold. The rest of the hardware - heatsink and fan, does it's best to take heat away from the 'hot' side of the TEC device. How well it does this depends on a number of factors. Personally, I wouldn't, and never have, attempted to run a cooled camera at 100% power. TEC devices are semiconductors and can quite easily fail under certain conditions. Louise

Spec for the pro version is here https://www.firstlightoptics.com/zwo-cameras/zwo-asi071mc-pro-usb-30-cooled-colour-camera.html#specifications

I think most modern tecs have a delta of 40 deg. So at 30 deg you should be able to reach -10 deg. Therefore you shouldn't set your target to lower. The camera should be able to reach -10 but it will draw a max current. There may also be a maximum ambient operating temperature and humidity specified by the manufacturer. If you're unhappy with the camera you could ask the seller for a refund. Louise

What's your ambient night time temperature?

Hi Imaging life would have been much easier with a shorter focal length scope but too late now... You'll certainly want a focal reducer e.g https://www.firstlightoptics.com/reducersflatteners/celestron-f63-focal-reducer.html (if you don't have an Edge model). Louise

Hi Gina I have a qhy183m cmos camera. Compared to either my Atik383l+ ccd or my qhy8l osc ccd, it's much more sensitive, less noisy and much quicker to download images. But both ccds have bigger pixels and are 16 bit, so much greater well depth, plus can do proper binning, of course. You can look at the graphs of gain v dynamic range/well depth and noise. There is an optimum (not sure what it is for the asi1600). I generally find I get better (=nicer) images if I keep the gain very low on the 183 as dynamic range falls off pretty rapidly with increased gain. However, I'll wack up the gain to aid focusing and platesolving then reduce it back to the low value for actual imaging. The 183m is low noise and high QE (84% I think) - not sure how that compares to the 1600. I have to admit I was quite sceptical about cmos cameras because of them being only 12 bit but my one can still produce quite nice images - as everyone else's cooled cmos cameras do too, of course! Louise

Hi As you have a guider I wouldn't bother with PEC. I wouldn't bother with st4 either - just connect to your guide cam via usb. I use ascom, StellariumScope and Stellarium with my AVX. PHD2 for guiding and whatever is your favourite image capturing software. Keep it simples! Louise

I don't really want to join another group or have to sit and learn another piece of software... I just don't have the patience! I'm getting old and the world seems to be becoming a difficult and frustrating place to deal with. Just trying to see what I'm doing is frustrating and challenging. Sigh. I might try another star and see if that's any better. It will have to wait for a while (maybe December) now as I've got too many other (non-astro) things I have to do. Louise

Had another go with the same data. It came out looking a bit different. I edited the original fits image in Gimp 2.10 - flipped, rotated a bit and cropped and saved as .fits again. But, try as I might, I couldn't get RSpec to read the file in again. There must be some compatibility issue. So saved it as a jpeg and used that. The RSpec was driving me crazy again especially with things like trying to resize the spectrum in the RSpec window but other things also. Anyway, here's the final output: It's smoother but, as I say, also looks different.... The Y-scales have come out different, as have some of the peaks. I've no idea why! I'm sure there is an explanation but if results aren't consistent, it's not reassuring. Louise

Yes, they should have both been aligned along the RA axis. I obviously rushed it... I'll have a play with the images I've got, when I have time. Louise

I had it approximately aligned with RA on purpose but didn't realise needing to rotate the image would be such a problem especially as the rotate facility is built-in. It will likely be several weeks (or >month(s)!) before I'm likely to be able to have another go. Do you think using the SA100 with a longer focal length will be better? I calculated that the dispersion would be ~16A rather than the current 5.4A. The Atik is not half as sensitive as the QHY183m, though, and is noisier to boot. Louise

Oh ok, thanks, Robin. I might try flipping and rotating it in Gimp. Can also crop it too. It might be that the 20MP image was affecting the operation of RSpec - who knows. Louise

Gosh, that's a lot smoother! How did you do it without rotating? I had thought of rotating the original image (or flipping it horizontally and hence rotating it less) but wasn't sure if that would make much difference? Louise

Yeah, I think it's too complex to do all the calibration etc for outreach. I think you're maybe limited to just publicly showing either the raw image with spectrum in colour or maybe the uncalibrated one with colour. I also suspect that even if properly processed the SA100 low resolution means the results could be a bit underwhelming. I'll see what I can do with it though. Louise

This is the image I used: This is the fainter image from the opposite side: You can barely see this one! Louise

Hi Pretty sure - I don't think there was anything else nearby and wouldn't expect to see anything else with only 2s exposures. I'll have a look at some of the stars I did longer exposures with when I get the chance. Dentist appt. tomorrow then I have a load of homework to do. Louise

Yeah, I thought it seemed noisy too. And, yes, I did have to rotate the image - by 209 deg! I suppose all the stars I did will be like that then Oh well. At the moment the SA100 is mounted in a TS filter changer but the grating is too deep to allow removing the drawyer, so I'll have to disassemble in order to rotate it to the right position. That's a bit annoying... I might transfer the SA100 to the 115mm APO + Atik 383l+ That might give better results but the guiding won't be so good ant the Atik is rather slow. But at least it has a filter wheel - hope there's no problems fitting the SA100 viaa a 2" adapter. If that doesn't work I'll probably give up on it again! Thanks Louise

Ta for the encouragement! It's actually not my first go - I did do a bit a couple of years ago but got a bit frustrated with it and also didn't have the time. It's quite easy and quick to acquire spectra once you have good focus etc. But the processing is a little long winded. Having said that, like many things, I expect it will get quicker and easier the more I do. I have a number of stars to process, Castor was just the first. I acquired images of mostly A-type stars but also did some others. Good luck if you have a go. Louise

I eventually arrived at this spectrum of 66 Gem (Castor). The RSpec software was ok-ish but it didn't always do what I expected it to and it's never clear how to save your work. There's no back button! Very annoying at times! According to the tutorials I should have been able to left click and draw a box around a section of the spectrum but I wasn't able to do that . The y-scaling tended to go a bit crazy on me... Anyway, here are the spectra: 1. Pre instrument response normalisation: 2. Post Instrument Response: I used a stacked image - 61 x 2s. Maybe I'll have another go via the individual images - if I can get in the mood! Castor is a spectral type A1V (The Stellarium details say 'A1.5IV'). However, there are no actual A1 types in the RSpec reference library so I wasn't sure about the calibration. I got the Balmer lines to line up with the features. My H-Beta line was to the right of the main peak rather than to the left as in the Vega example. I would have imaged Vega if only my scope could see it! Vega is a type A1V - not sure if the slight difference in spectral types accounts for the differences? Though maybe the star in the tutorial video wasn't actually Vega?!! I didn't think at the time but Castor is a double star. However, it's probably of no consequence as Castor itself is so bright. Anyways, any constructive criticism gratefully received Louise

Ah, I thought you meant as per the video tutorial where the guy adjusts the focus in RSpec whilst capturing an avi. Anyway, I've had a go. I think some of the ones earlier in the evening were maybe not so well focused - looked more like a smear... I'll try and download the RSpec sometime this week and have a look at what I've managed to get tonight. I was quite surprised - and pleased! - that I could still platesolve even with the SA100 in place. I'll post an update when I've looked at the data Louise