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Have you thought about mounting a camera at the prime focus and doing away with the secondary altogether?
No worries about light-loss from multiple reflections.
Might not work, but if you are experimenting anyway, perhaps this might be worth a try.
I observed some targets from Roger’s most recent alert list. There were a few issues which I believe are now mostly sorted. In particular, Astrometrica would not play ball so I used my regular BAA-VSS pipeline. To do that, I had to build my own comparison star photometry file from the APASS catalogue, itself downloaded from a link provided by Roger. The script to make that file is available on request.
First result: at 2021-07-07 23:00, Gaia21au was CV=16.72 ± 0.05 and V=17.00 ±0.10
Some of the fields are very crowded and aperture photometry likely won’t be sufficient. PSF fitting, e.g. by DAOPHOT should work but that will be another can of worms to explore.
Anyone in the VSS wish to comment? In particular, should these observations be uploaded to the database?
“Yes, I can print pages from that though I still get the encrypted message if I download and use Acrobat DC (Win 10).” Aah, that suggests that your browser will print anything it is displaying but that Acrobat is honouring the content creator’s wishes. I will try to look into it.
Good to see you have an effective if possibly crude work-around.
Added in edit:
A very quick search on “printing password protected pdf” turned up numerous sites, such as these two. https://passper.imyfone.com/pdf/how-to-print-password-protected-pdf/ & https://www.maketecheasier.com/recover-lost-pdf-passwords-linux/
I can’t vouch for either of them.
Thanks. I will give that one a try when we have a decent night here. A calima has filled the sky with very fine dust 8-(
Would an off-axis stop help for bright objects, do you think? It would reduce the sensitivity and I generally dislike throwing away photons.
If I get anywhere I may consider using a more conventional spectrograph, but that is serious money to spend on a whim, hence the SA.
Thanks, Robin, for getting back to me so quickly.
I used the calculator to determine that with my equipment the SA200 was the better bet. Your advice: “On telescopes with a larger aperture and a longer focal length, the dispersion of the SA100 can be insufficient to achieve the best results.” tallied well with my set-up — a 0.4m f/6.5 Dilworth with a SX imaging train. Plugging the relevant numbers into the calculator seemed to bear out that advice.
I will check out the other links too.
My first scientific observation since returning to La Palma and to a whole host of instrumental and computer problems.
V=16.85 ± 0.04 at JD 2459400.480961
There seems to be another wrong-link misfeature.
Creating a new forum topic and clicking preview works fine. However, then clicking on the “Read more” link took me to the page “Filters for visual observing of the Moon and planets”.
Thanks, Paul.
We agree that a line needs to be drawn. We agree that additions to the tag table, if any, should be as easy to do as possible.
I could very easily write a sequence of SQL statements similar to “INSERT INTO tags VALUES (DEFAULT, ‘name’)” if the database schema were available to me, not least because I have exactly that kind of list in the code which creates my own image database. Your work would then consist solely of eyeballing it for structural correctness and then running the SQL on the database.
Thanks. Now updated that one using the date of the last image. The time was left at 00:00:00 UTC to indicate that any greater precision is unjustified for an observation which took 349 days to complete. (Incidentally, should the time of observation field be pre-filled with that value? It seems to make more sense to me than to have it set to the time of uploading.)
Would you consider running the suggested SQL query to see how many other examples exist? If there are only a (relatively) few perhaps a web page could be created with a list of (username, url) pairs. It would then be up to individuals to update their own observations and would require no further action on you part except, perhaps, re-creating the table every few months.
Sorry to take so long to spot this one but it was prompted by looking at a recent observation by David Strange.
https://britastro.org/observations/observation.php?id=20200911_170000_2e604aed4f94042d is the consequence of migrating my https://britastro.org/node/24192
According to the migrated page, the upload occurred a few minutes before the observation was made! The original records the observation time as 11/09/2020 – 18:00 and does not record the upload time.
According to my paper records,the two images in the animated GIF were taken on 2019-08-30 and 2020-08-13.
Not sure what to do here. I can edit the observation time fields but not the upload time. Given that the images were taken in two separate years and only one date-time field can be entered, perhaps that for the last image in the series should be used but advice is welcome.
Regardless of this particular case, perhaps there may be other examples in the database. A simple SQL query should dig out any if they exist.
I’ve not used Perl anywhere near that ancient in a very long time and have never had significant problems in the last 20 years, despite having written at least 20k lines of Perl over that time. You got caught up in the Perl 4 / Perl 5 changeover, which was at least as big as the Python 2.x – 3.x transition. People, including myself, are still suffering from that one 18 months after 2.x EOL and several years after the writing appeared on the wall.
Although religious arguments are great fun I suggest that we should take this one elsewhere and return the thread to matters astronomical.
Thanks, but I already have it myself. Anyway, the Pi has a fully functional C compiler and Perl interpreter which are my languages of choice and how I implement such code on all my other Linux boxen..
On further thought, I also have the Pi IR-enabled camera so no need for a web cam, USB connection, fancy interfacing software, etc.
Now wondering how much extra it would cost to go the whole hog and put a plate solver into the system. A Pi with a 32G SSD would have easily enough power to run it. Use a phone as a display and controller over wifi. Optics are 50mm refractor and web cam on a standard finder bracket, to which the Pi would also be attached. A pity a USB cable would still be needed but a rechargeable battery could presumably be attached to the mount somewhere, even on a Dob.
Major development cost would be writing software.
Hmm. I have a Pi-3 over in La Palma. Might have a play when I return there.
We did consider using Uranometria as a guide to star hopping, but I’m afraid the Bodleian didn’t seem keen to lend out their copy ….
How faint do you need to go? Freely available charts reach mag 7. Here is one of Orion, for example, and another around the NCP.
Something which worked well for us back in the day was to get a 10 foot long cast iron pipe, complete with drilled flanges at each end, from a scrap yard. It was painted inside and out with bituminous paint. A hole of suitable dimensions was dug so that a plug of concrete 3 feet thick and three in diameter could hold the bottom of the pipe, which was buried to slightly more than half its length. The inside of the pipe was then filled with sand. The top flange was ideal for attaching an equatorial head.
The fundamental vibration mode and small harmonics were heavily damped by the concrete and through being clamped with back-filled sand. The internal sand quenched high frequency vibrations very effectively.
It was possible to have one person placing fingertips very gently on one side of the pipe while another hit it as hard as possible with a length of 2×3 on the opposite side and still feel no vibrations.
I saw a weather report yesterday. Unfortunately I failed to save the URL. It would be nice to have a more authoritative source than that given below but …
https://www.express.co.uk/news/science/1427137/space-weather-forecast-solar-storm-aurora-evg
Does this help? Being an Oxford man I went to the Bod, which led me to this:
An interlibrary loan may be possible. Worth asking, anyway.
