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Old 09-05-2020, 07:30 PM
Heian (Mark)
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Starting again

Hi all,
after a long, long break from astronomy and spectroscopy, I have made an effort to get back into it again. The attached images are from some Be stars and Gamma Velorum taken last night.

The images were taken through the SA100 / Meade dsi3 combination attached to a 200mm f/5 reflector. The images have only had simple processing with no instrument response correction through BASS.

This combo gives approx 29A/px.

The next step will be to re-learn the software.

Any comments would be welcome
Attached Thumbnails
Click for full-size image (Gamma Velorum.jpg)
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Click for full-size image (p Car.jpg)
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Click for full-size image (QY Car.jpg)
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  #2  
Old 10-05-2020, 01:36 PM
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jjjnettie (Jeanette)
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Good to hear you're back on the wagon
Comet Swan has been my inspiration to start again. Relearning the software has been a painful and time consuming experience.
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Old 12-05-2020, 11:39 AM
Saturnine (Jeff)
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Great to hear you're getting back out into the dark again Mark, can't say that I fully understand spectroscopy but someones got to do it, otherwise we would never learn anything.
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Old 12-05-2020, 04:38 PM
Heian (Mark)
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Thanks Jeff and jjjnettie,
I did some more image capture on Sat night, but with some mods to the setup. I've extended the SA100 / CCD spacing and added a grism to the setup.
I'm now getting in the order of 8.9A/px, compared to the original 29A/px.

I went back and re-imaged a target from first night again. It's easy to see that the curve is not as "lumpy" as it was. The target was QY Carina. The slightly higher resolution is on file QY Car spectrum.png"

I've also included a spectrum of Eta Carina for good measure

cheers
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Click for full-size image (QY Car spectrum.png)
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Click for full-size image (Eta Car spectrum.png)
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Old 26-05-2020, 05:57 PM
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Merlin66 (Ken)
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Mark,
Sorry mate, I missed your post!
Well done you have some interesting results there.
The next step is to image an A type star and develop an IR correction curve.
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Old 27-05-2020, 11:46 AM
Heian (Mark)
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Hi Ken,
i did get a spectra of Alpha Volans, and A2v star to do just that but I was getting what I thought an unusual result when I divided my capture with A2v reference in the BASS software.

I posted a question on the group.IO site and John and yourself commented on the next step. I just haven't done it yet.

From what I can see, the B+W chip in the DSi3 collects further into the blue end than other CCD's I have imaged with.
I've added the partially processed images.
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Click for full-size image (alpha vols A2v.png)
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Click for full-size image (alpha vols A2v division.png)
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Old 27-05-2020, 01:01 PM
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Merlin66 (Ken)
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Mark,
yes I remember now...
Just crop below 370 and above 750nm and see how you go.
Ken
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Old 28-05-2020, 04:30 PM
Heian (Mark)
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Hi Ken,
thanks for the offer of assistance with my issue of the IR for the spectra of Alpha Volans.
I've added the file as a jpg, which is the only one I could get to load.

I'll keep plugging away to see if i can get it to work after all...
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Old 03-06-2020, 08:54 AM
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Merlin66 (Ken)
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Mark,
PM sent.
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Old 03-06-2020, 01:37 PM
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Good stuff Mark, glad to see you're making progress, congratulations! I'm following a similar curve to you at the moment (no pun intended!). While I've had an SA100 for almost 15 years and have taken vast numbers of spectra (particularly of novae and comets), I've never taken spectroscopy any further than raw, uncorrected spectra. Happy just to have spectra that broadly categorised objects and to leave the hard work to the professionals (and keen amateurs)!

However with arrival of some new equipment at the start of the year and with the subsequent lockdown, I decided to explore spectroscopy a little deeper. So I've attached my first ever spectrum corrected for instrument response! Nothing flash, just Alnair (Alpha Gruis), but I'm immensely proud of it & can't stop looking at it LOL! I normally use BassProject but used RSpec only because I found YouTube instructional videos for the processing.

The other spectrum is of comet C/2020 F8 (SWAN) taken early last month. So far it has resisted my attempts at correcting for instrument response but I haven't given up yet (mind you I've generated some weird and wonderful looking graphs! ). I'm using a ZWO colour camera - like most things it's a compromise. Not good for a lot of things I do but then a mono camera won't produce colour comet shots without a lot of work. Great to have the extended wavelength range, particularly for the main comet CN line at 388.3nm (not gettable with standard DSLR).

Anyway, good luck with it Mark and keep posting on your progress. Thanks too Ken, you're always willing to help people and provide them with great advice.

Cheers -
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Click for full-size image (Alnair spectrum, 28 May 2020 text to epsilon.jpg)
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Click for full-size image (C2020 F8 spectrum, 04 May 2020 text RSpec sm.jpg)
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Old 03-06-2020, 01:52 PM
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Merlin66 (Ken)
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Rob,
After all these years.....a calibrated spectrum! Well done.
If you have an IR curve you can use it to correct any other spectrum taken with the same set-up. There may be slight atmospheric correction differences, but close enough.
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Old 04-06-2020, 06:32 AM
Heian (Mark)
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Hi Rob,
nice results
I see you are getting about 2.5A/px, which I believe is pretty good for a SA100.
Do you mind commenting on the setup you used to get the spectra of Alpha Grus?
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Old 04-06-2020, 12:16 PM
Rob_K
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Thanks Mark. As they say, a picture's worth a thousand words so I've attached a couple of shots. I didn't hook the camera up, but in action of course there are cables, battery and a laptop in play. This set-up is limited in that the camera/lens weight is too much for the tracker unless it is fairly well balanced. I've only used this set-up for the two spectra I posted - I really need to use my telescope & mount if I want to train this camera on a wide variety of sky positions.

The Alnair spectrum is a 1909-pixel strip on the original 4944x3284 px image, hence at 4700 length it represents 2.46/pixel.

Cheers -
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Last edited by Rob_K; 04-06-2020 at 12:54 PM. Reason: Mistake in image size!
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Old 04-06-2020, 12:57 PM
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Merlin66 (Ken)
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Rob,
Which camera?
Which Lens?
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Old 04-06-2020, 01:17 PM
Rob_K
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All on the annotated spectra Ken! Except that the 200mm lens is a Canon EF 200mm 1:2.8.

Cheers -
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Old 04-06-2020, 02:01 PM
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Merlin66 (Ken)
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Ahhh, OK. Got it!
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