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Also, if you use TSX for guiding you can view the guiding corrections sent to the mount (right click on the auto-guiding graph and select “graph corrections sent to mount”). Aggressiveness can be adjusted while guiding in TSX, so you can view the effect of changing the values by viewing the graphed corrections in real time (the green lines on the screen shot below).
Paul
Hi Tony,
Great work. How long did it take to print the main body at high infill? Was your printer screaming for mercy? 🙂
Paul
Hi John,
There are no fringing issues with the 414EX at low resolution, and I believe it is still the “CCD camera of choice” for the Alpy.
Paul
Hi Alun,
I often note to others that I have friends who spend more on golf than I do on astronomy, so unless you’re doing spectroscopy and playing golf you have nothing to worry about.
Great spectra too. 🙂
Paul
We have very long hot summers down here, which probably wreaks havoc on the seals when followed by cold wet winters (my gear lives permanently outside in an observatory). I’ve had two instances of ‘fogging’ this year, which have been remedied by replacing the desiccant tablet (after baking). If you’re interested, the Atik procedure is here:
https://www.atik-cameras.com/question/revive-old-desiccant-tablets/
Paul
Jack,
The fringe phenomena is not an issue at low resolution. Fortunately I have an Atik 314L+ on my Lhires. The best of both worlds it would seem.
Robin – thanks. Yes, the issue is one of gradual deterioration of a fixed image train, which is why David’s post has me thinking. It could also be all in my head 🙂
At this stage the ‘red’ end of my Alpy work is less important, so depending on my enthusiasm I may not bother doing much in the short term.
On a related theme, I’ve found that the Atik desiccant tablets need re-charging about twice a year at the moment (since 2014) with the 414 slightly more temperamental than the 314. I’m curious to know how others Atik owners fare with desiccant life.
Paul
I think I posted an image on this topic some time ago (light pollution lines that were not Na).
Generally, the software assisted sky background subtraction we use when processing spectral images pretty well mitigates all light pollution. I think it’s one of the best kept secrets of suburban spectroscopy (versus photometry and astrophotography).
Paul
Hi David,
I’ve seen a gradual deterioration of my ‘red’ lines with an Atik 414ex on an Alpy, and am close to investigating the problem to see whether it’s simple tuning or something more sinister as yours.
Were you able to see the film yourself on the surface of the cover glass using a magnifier after it had been pointed out to you – or had Terry already cleaned it? I’m wondering how ‘difficult’ it is to pick up.
Paul
I’m with Andy. Try imaging the bulb in a completely dark room (ie, with just the Neon lamp turned on) to eliminate other sources of light. If the ‘hump’ is still present, then it may well be the lamp itself.
What are the specifics of the neon “light bulb” you’re using?
Paul
The SWIFT observation is a really nice addition to this, and confirms yet again the increasing importance of small telescope / fast response amateur spectroscopy. With your permission I’d like to use this example in an up and coming presentation that I’m giving on the subject at UWA.
Paul
Hi Tony,
I’ve only had a cursory look at your workflow, but it looks pretty thorough to me.
The ultimate test of flux calibration accuracy is to compare your result with a standard. The CalSpec standards (some available in the ISIS database) can be use for such comparisons.
Paul
Although I can’t see VV Cep from my latitude, I’ve been following this project with great interest (having seen Ernst’s excellent presentation at the OHP in 2015 – my first exposure to this remarkable star). I think this is another example of great community involvement and coordination of observations (both here and on the ARAS channel) the value of which cannot be underestimated.
Keep up the great work Ernst, Jack and all.
Paul
Hi Steve,
I’m happy to oblige, though my attempts are not novel by any means, and I’m certainly no expert.
Nevertheless, I’ll write this up over the next week or so and let you know. I’m actually hoping for a break in the weather to improve on the data collected so far, though I have enough to share in the mean time. Stay tuned …
Paul
Hi all,
Just to close the loop on this; I ended up measuring the radial velocities of 3 planetary nebulae with published values ranging from -13 km/s to 194 km/s. I used PlotSpectra’s point and click measurement tool, averaging the velocities of the prominent H and OIII emission lines.
All three ended up within 15 km/s of the published values – which is closer to what I expected vs my original post on the matter. Of note, the spectra were hastily acquired (ie, resulting in low S/N) between rain and clouds.
I’ve attached a couple of profiles. Nebulium 😉 dominates these objects, as expected, and in the case of the attached NGC 6629, the black body profile of the hot central star appears (perhaps?) to be peaking through at shorter wavelengths, although I did not correct for instrument response (I mention this only as my other two show little sign of a central star via the continuum which could be targeting, or target). Despite the low resolution of the Alpy, there are some interesting differences in the features of the acquired profiles which I’m yet to fully investigate. NII 6583Å is clearly visible in NGC 6818, with its sibling on the other side of H-a not quite developed at this resolution.
A recommended activity for Alpy owners / beginners.
Thanks, Robin, for the links to the ISIS CCF information above.
Cheers,
Paul
Apologies to all. I’ve just revisited NGC6629 tonight and a quick processing has me at a much better result (+/- a few km/s). I suspect a mis-targeting or blunder in file naming. I’ll post some results in due course.
Sorry for the interruption.
Paul
I’ve been searching without success – I don’t suppose anyone has a link to Christian’s tutorial on using CCF in ISIS (I need a refresher).
Thanks all,
Paul
… can be found here (for anyone interested):
Schneider, S. E., Terzian, Y., Purgathofer, A., & Perinotto, M. (1983). Radial velocities of planetary nebulae. The Astrophysical Journal Supplement Series, 52, 399. http://doi.org/10.1086/190874
Though I thought operating at about 500 Å/mm would get me within 50 km/s, clearly there are other factors at play. Fortunately I also own a Lhires (I just need clear weather).
Paul
