Hi!

I'm reconnecting to this with reference to the keywords CRVAL. Robert, in one of your posted FITS-headers, these keywords are present. Not in the others. I do NOT get these keywords (I'd would have been nice though). How come they are in one of your headers? Do you still get them?

How about the rest of you - anyone getting these keywords? I did not think they were added at all by EKOS.

Magnus

Magnus,

I saw your post last night while I was taking some spec data. I use a Lodestar as my guiding camera while my primary camera is gathering spectra. I was pointing at rather bright objects so I had not done a plate solve. When I took a picture with the Lodestar and looked at the FITS header, the header had the usual items you would expect, but no CRVAL, etc.

So I did a plate solve and then took another pic with the Lodestar. Now I had all kinds of stuff as you can see below.

CRVAL1 = 326.69596952 / CRVAL1
CRVAL2 = 49.319472474 / CRVAL2
RADECSYS= 'FK5 ' / RADECSYS
CTYPE1 = 'RA---TAN' / CTYPE1
CTYPE2 = 'DEC--TAN' / CTYPE2
CRPIX1 = 188. / CRPIX1
CRPIX2 = 145. / CRPIX2
SECPIX1 = 2.0837599675 / SECPIX1
SECPIX2 = 2.011334871 / SECPIX2
CDELT1 = 0.00057882221321 / CDELT1
CDELT2 = 0.00055870413083 / CDELT2
CROTA1 = 9.3594641181 / CROTA1
CROTA2 = 9.3594641181 / CROTA2

Probably you and I would both like to see that data in our primary camera header when doing spec work but that's not likely to happen. When I go back to doing variable star work where my primary (ZWO) camera does plate solving, I'm expecting to see these kinds of details.

I see you have a Star'Ex. Did you build that using 3D printing? I've looked at the instructions on how to do it but I've never done 3D printing and I figure this is something I could really botch.

Hi!

Yes, it would be very good if the CRVAL keyword where in the fits header - for example, SpecINTI relies on this for computing atmospheric extinction.

I was surprised to see it in your header, because I was under the impression that Ekos did not produce it at all. Now, looking through my own photometric images, I do find it there too. But not in my spectra. For photometry, the main camera does the platesolve, for spectroscopy, I have a separate "positioning guide scope" doing it - in its own imaging train. So I do not use the guider for platesolve, never worked for me due to small FOV with my C8 and C11.

What version of Kstars do you run? I'm using 3.6.4 stable on Stellarmate.

Concerning the StarEx: I have indeed printed it myself, and also the Lowspec that I use (first bought one second hand but decided I wanted to print it myself). After beginning with 3D-printing I actually no longer understand how to do amateur astronomy without a printer jokes aside, it takes some time to acquire skill sufficient to print a good spectrograph but it is not very difficult. But if you don't want to print, there are commercial sources that can print for you. Or maybe some other amateur - ask on the Sol'Ex mailing list What kind of spectroscope du you currently use?

Magnus

Ah! I was thinking, "I wonder if Magnus is using specINIT" because I know they want to see the CRVAL numbers either in the header or the configuration file. I just started "using" it about a month ago and am excited about what it can do, especially if we can eliminate the need to take a Cal star for every observation. I just took some data on HD207330, the example star for his low res example, to see if I can come anywhere close to Buil's results.

My spectrometer is from SX Xpress. It's a low res instrument (max R is 2000) and uses mirrors as opposed to lenses so it can reach into the UV and IR better than most. Now, given cameras have almost no capability in the UV, the near IR is probably all I can do. The camera has a built-in Lodestar for pointing and a built-in Argon/Neon cal lamp. There's a new version that allows remote control of the functions that are now manual (like having to go into the dome to turn on/off the cal lamp) and should I upgrade or try a Star'Ex.

Which camera do you use for the spectra? Is it a CMOS? I'm looking at spectrum examples trying to determine what is the optimum gain value so that I capture the entire spectrum, in other words, how many f/stops do I need.

CS,
Bob

Forgot to mention I'm running kstars 3.6.4 on both my computer in the control room and on StellarMate in the dome.

Hi!

That looks like an interesting spectroscope, compact design, if I get it right. I use the Lowspec for low resolution spectra, which is what I do most, and I like the compact design of that too - although it is somewhat less easy to focus the guidecam as compared to the StarEx. I use the StarEx for high resolution spectra, just nu feeling confident enough with it to just use it. Neither are remotely controlled - that would be nice. I'm looking into how to make calibration lamp remotely controlled. And the SpecINTI allows "lateral mode" calibration, that would be really handy - but then the lamp must be software controlled. I use a CCD for my Lowspec, an Atik 314L+, and a CMOS for the StarEx, a QHY183m. I'm also not sure about the gain values for the CMOS. For the moment, I use gain 10 to get as large full well as posslble (for bright targets) and to only have one set of darks and flats. I can imagine having higher gain would be good for fainter targets though. Unfortunately, QHY and ZWO use different logics for their gain values, as I understand it, so Christian Buil's recommendations based on his ASI183 are not useable for me.

And back to the header issues: Last night, spectrum of R Leo using my SM with KStars 3.6.4, I get these headers from the StarEx:

SIMPLE = T / file does conform to FITS standard
BITPIX = 16 / number of bits per data pixel
NAXIS = 2 / number of data axes
NAXIS1 = 5544 / length of data axis 1
NAXIS2 = 1000 / length of data axis 2
EXTEND = T / FITS dataset may contain extensions
COMMENT FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
BZERO = 32768 / offset data range to that of unsigned short
BSCALE = 1 / default scaling factor
ROWORDER= 'TOP-DOWN' / Row Order
INSTRUME= 'QHY CCD QHY183M-9b51164' / CCD Name
TELESCOP= 'Celestron NexStar' / Telescope name
EXPTIME = 3.000000E+02 / Total Exposure Time (s)
CCD-TEMP= -1.000E+01 / CCD Temperature (Celsius)
PIXSIZE1= 2.400000E+00 / Pixel Size 1 (microns)
PIXSIZE2= 2.400000E+00 / Pixel Size 2 (microns)
XBINNING= 1 / Binning factor in width
YBINNING= 1 / Binning factor in height
XPIXSZ = 2.400000E+00 / X binned pixel size in microns
YPIXSZ = 2.400000E+00 / Y binned pixel size in microns
FRAME = 'Light ' / Frame Type
IMAGETYP= 'Light Frame' / Frame Type
FOCALLEN= 2.000E+03 / Focal Length (mm)
APTDIA = 2.790E+02 / Telescope diameter (mm)
FOCUSPOS= 700 / Focus position in steps
FOCUSTEM= 2.000E+01 / Focuser temperature in degrees C
SCALE = 2.475600E-01 / arcsecs per pixel
SITELAT = 5.554806E+01 / Latitude of the imaging site in degrees
SITELONG= 1.336472E+01 / Longitude of the imaging site in degrees
AIRMASS = 1.483571E+00 / Airmass
OBJCTAZ = 2.111180E+02 / Azimuth of center of image in Degrees
OBJCTALT= 4.233853E+01 / Altitude of center of image in Degrees
OBJCTRA = ' 9 46 10.43' / Object J2000 RA in Hours
OBJCTDEC= '11 29 40.85' / Object J2000 DEC in Degrees
RA = 1.465435E+02 / Object J2000 RA in Degrees
DEC = 1.149468E+01 / Object J2000 DEC in Degrees
PIERSIDE= 'EAST ' / East, looking West
EQUINOX = 2000 / Equinox
DATE-OBS= '2023-04-23T20:14:13.101' / UTC start date of observation
COMMENT Generated by INDI
GAIN = 1.000E+01 / Gain
OFFSET = 2.000E+01 / Offset
OBJECT = 'R Leo ' / Object
END

So information about where it is pointing is obviously there, but not the keywords. An hour later, doing photometry, there are some 10 lines more, including the CRVAL. I guess this is a snooping issue.

Magnus

Magnus,

Great stuff. Lots to unpack.

When you were doing photometry, did you do a plate solve before you got all the "extra values?" Because that's what happened when using the Lodestar tracker when doing spectrometry. Before plate solving, I got none of the CRVAL etc numbers. After plate solve, bingo. So it may not be a matter of snooping.

However, it occurred to me -- suppose I have my camera capturing the spectra (ZWO) snoop on my Lodestar guiding camera. Would the ZWO pick-up the values from the Lodestar? Cloudy weather tonight in southwest New Mexico so I can't give it a try.

Gain. I also do photometry on variable stars and, if you look at a map that shows the known comparison stars, they're all within 3 to 4 mag of the target. Let's assume 5 mag which is a factor of 100. Give a margin of error and an f/stop of 8 => 256. I can run my ZWO at a "gain" of 450 and still have 9 f/stops. I put "gain" in quotes because it seems like the accepted norm is to quote gain in terms of tenths of a dB, at least in the ZWO world. Now, I'm a newbie at all this so there could be a valid reason not to use high gains when doing variable star work. Yes, there are some stars that vary wildly (10 mag or more) so you need to be flexible. But, when I look at the submissions from other observers, I can't help but wonder why they're using gains with 13 f/stops.

As for the Star'Ex, I want to continue to do low res spectrometry just because it interests me; no other logical reason. I look at the files included in the specINTI documentation and, for their low res star example, they're getting 40 - 50k counts in 30 sec where as I'm getting maybe 30k in an exposure of 8 minutes! Plus they're using a 10' RC and I have a 12'. I think the answer is simply a bigger tube. The entrance to my spectrometer is about 5 mm. Looking at the pictures on the web it appears Star'Ex is using a significantly larger aperture. I was doing some web searching and I see where a firm is selling the Sol'Ex non-optical constructs for about 160 Euros. The optics for the low res Star'Ex are another approx 550 Euros. Haven't found all the right components as of now. But, the idea that I can have a spectrometer with the capability I'm seeing in the examples from C. Buil for about $1k dollars is why I'm still up at 0200 local, and not observing. You are much more experienced in all this than I; tell me if I'm missing something.

I'll send you some examples of photometry headers tomorrow when i go out to the control room.

Cheers,
Bob

Here is the FITS header from some photometry work done earlier this year.

SIMPLE = T / file does conform to FITS standard
BITPIX = 16
NAXIS = 2
NAXIS1 = 3120
NAXIS2 = 2088
EXTEND = T / FITS dataset may contain extensions
COMMENT FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
BZERO = 32768
BSCALE = 1
ROWORDER= 'TOP-DOWN' / Row Order
INSTRUME= 'ZWO CCD ASI2600MM Pro' / CCD Name
TELESCOP= 'Celestron CGX' / Telescope name
OBSERVER= 'Unknown ' / Observer name
OBJECT = 'AB Aur' / Object name
EXPTIME = 3.000000E+00 / Total Exposure Time (s)
CCD-TEMP= -1.980E+01 / CCD Temperature (Celsius)
PIXSIZE1= 3.760000E+00 / Pixel Size 1 (microns)
PIXSIZE2= 3.760000E+00 / Pixel Size 2 (microns)
XBINNING= 2 / Binning factor in width
YBINNING= 2 / Binning factor in height
XPIXSZ = 7.520000E+00 / X binned pixel size in microns
YPIXSZ = 7.520000E+00 / Y binned pixel size in microns
FRAME = 'Light ' / Frame Type
IMAGETYP= 'Light Frame' / Frame Type
FILTER = 'Vis ' / Filter
FOCALLEN= 1.702E+03 / Focal Length (mm)
APTDIA = 3.040E+02 / Telescope diameter (mm)
FOCUSPOS= 25600 / Focus position in steps
FOCUSTEM= -5.500E+00 / Focuser temperature in degrees C
SCALE = 9.112876E-01 / arcsecs per pixel
SITELAT = 3.248750E+01 / Latitude of the imaging site in degrees
SITELONG= -1.079844E+02 / Longitude of the imaging site in degrees
AIRMASS = 1.000542E+00 / Airmass
OBJCTAZ = 1.834659E+02 / Azimuth of center of image in Degrees
OBJCTALT= 8.811306E+01 / Altitude of center of image in Degrees
OBJCTRA = ' 4 57 08.62' / Object J2000 RA in Hours
OBJCTDEC= '30 36 11.98' / Object J2000 DEC in Degrees
RA = 7.428592E+01 / Object J2000 RA in Degrees
DEC = 3.060333E+01 / Object J2000 DEC in Degrees
PIERSIDE= 'EAST ' / East, looking West
EQUINOX = 2000 / Equinox
CRVAL1 = 7.4285924161E+01 / CRVAL1
CRVAL2 = 3.0603329021E+01 / CRVAL1
RADECSYS= 'FK5 ' / RADECSYS
CTYPE1 = 'RA---TAN' / CTYPE1
CTYPE2 = 'DEC--TAN' / CTYPE2
CRPIX1 = 1.5600000000E+03 / CRPIX1
CRPIX2 = 1.0440000000E+03 / CRPIX2
SECPIX1 = 9.1128759167E-01 / SECPIX1
SECPIX2 = 9.1128759167E-01 / SECPIX2
CDELT1 = 2.5313544213E-04 / CDELT1
CDELT2 = 2.5313544213E-04 / CDELT2
CROTA1 = 5.0870800305E+01 / CROTA1
CROTA2 = 5.0870800305E+01 / CROTA2
DATE-OBS= '2000-01-22T04:06:14.086' / UTC start date of observation
COMMENT Generated by INDI
GAIN = 300. / Gain
OFFSET = 50. / Offset
END

Hi!

Yes, there's the full set of keywords, like in mine when doing photometry. It seems to me as if the issue is which camera does the platesolving. Jasem says he'll be back on this in two weeks time, that's very good.

Concerning the spectrographs - I'm not sure I follow you here, about tubes and entrance diameters. In my mind, what matters most here are if the spectroscope is very well collimated (otherwise light is lost) and how well you are able to position the star on the slit. And of course slit width. I tend to use 20 um on my Lowspec and 23 on my StarEx. If you use SimSpec, the spreadsheet, you can learn at lot about these parameters.

As for gain: I go for as large full well as possible. I used to use higher gain, but experienced some comparison stars to become saturated at times. WIth a gain of 20 on my WHY283m, I have not experienced that. I don't know how to see what gain others use though. But I must confess that I don't really understand much about gain - I just trust experience and my expert friends

Magnus

Magnus,

Gain is like ISO on a digital camera. The key is that you know what works, and what causes saturation.

I tried having my main (spec) camera snoop on my Lodestar guide camera to see if the main camera would pick-up the CRVALs from the Lodestar. No such luck, not that I was expecting it to work.

Do you know why the insistence om getting values labeled CRVAL1 and CRVAL2? Those are RA/Dec values in decimal degrees and, in our FITS headers, those values differ from the decimal degree values of RA/Dec maybe at the 8th decimal place.

And then there is Aerosol Optical Depth. C. Buil gives a value of 0.04 for a dry desert like here in s/w New Mexico. There are lots of days where we get high winds that die off at sunset, but you can see quite a bit of dust in the air. Does that contribute to AOD?

More research to do.

Bob

Hope they don't mind hi-jacking this thread for a question about specINTI.

Magnus -- I cannot get specINTI to "read" my calib files, any of them. The lines are well defined with more amplitude than what Christian has in his example files, I know the pixel of a line to a gnat's eyelash. But every time the program gets to the Calibration phase, it hangs, even if I specify only one pixel/wavelength combination.

Any thoughts?

Thanks,
Bob

Hi Bob!

Tough one, with the calibration lines. You should post the question together with your files (a link to the folder you use as working folder in SpecINTI) to the SolEx group on Groups.io!

I'm far from an expert on SpecINTI, but I can imagine a lot of reasons, things that might be off in your configuration file (I speak from experience here......).

Best,

Magnus