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The dimmed spectrum divided by the current spectrum (green)
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The H alpha emission I mentioned in the VSSC article on RW Cep (and referenced in the paper) has also reduced in the past 3 months as the brightness increased so it looks like it is associated with the dimming.
Cheers
RobinAttachments:
Too low for a spectrum from me but here is one by Christian Buil this morning
https://groups.io/g/Solex-project/topic/101209364
The usual emission bands but not much dust and no obvious sodium despite it being close enough to the sun, at a similar distance to this spectrum of 2020 F3
https://britastro.org/observations/observation.php?id=20200713_224000_2e77e0992eb70386Cheers
RobinAn interesting article on SN 2023ixf. (Well known supernova expert Prof Alex Filippenko was showing people M101 at a star party 11 hours before discovery but did not spot it !)
https://news.berkeley.edu/2023/08/29/releases-20230828-6895045
(Hat tip to Rigel7 on cloudynights for this)Cheers
RobinI managed to squeeze in a high resolution spectrum last night in twilight before it dipped into some trees. The decreasing Equivalent Width of the H alpha emission line reported in ATel #16214
https://www.astronomerstelegram.org/?read=16214
is confirmed by the spectra in the BAA database.Cheers
RobinAttachments:
If it follows the usual IIP type trend I expect it will now continue in a shallow decline dependent on radioactive decay
Robin
I see from the light curve the slow steady decline (~2 magnitudes in V over 70 days) has come to an end and the brightness is now dropping rapidly (~1.5 magnitudes in 12 days) This behaviour is similar to that seen in type II-P supernova following the plateau period so SN 2023ixf may have characteristics of both type II-L and II-P, similar to supernova like 2013by discussed in this paper for example
https://arxiv.org/abs/1501.06491v2Cheers
RobinI guess the noise floor in the signal received at Voyager must be pretty high, aimed so close to the Sun ?
Voyager 2 is currently around 160au away so the Earth is always within 0.35 deg of the Sun
That prompted me to grab a virtual pencil and back of envelope. So to the unaided eye from there the Sun appears star-like (unresolved at just ~12 arcsec diameter) and ~mag -15.7, ~15x brighter than the full moon.
I like the way NASA phrase it as a “Communications Pause”
https://blogs.nasa.gov/sunspot/2023/07/
Though the Independent is reporting that it can still be heard at least
https://www.independent.co.uk/news/ap-earth-nasa-cape-canaveral-california-b2385612.htmlMartin Lewis takes some absolutely superb planetary images with his Dobsonian mounted telescopes. The rings of Uranus and surface detail on each of Ganymede, Mercury, and Venus are among some of his achievements.
But the list is supposed to be the best telescopes for astrophotography. I doubt if you polled astrophotographers (planetary or deep sky) they they would put this scope as the second best for astrophotography (or for that matter the one placed top of the list.)
Does someone get a payment if you click though to amazon on these links ?
It is difficult to know where to start. The website is riddled with misleading nonsense. For example here
https://astroimagery.com/equipment/telescopes/best-telescope-for-astrophotography/#research-what-telescope-would-you-recommend-for-astrophotography
in positions 2 and 7 here you have a Dobsonian mounted scopes which are not suitable for astrophotography and the description does not match the scope.I apologise if I am wrong but the main purpose of this website appears to make money not to inform.
Robin
How do I enable blue tab ‘Mr Jack Martin wrote’?
Highlight the text you want to quote with the mouse and click “QUOTE” instead of “REPLY” on the message you are replying to
See also this thread
https://britastro.org/forums/topic/software-for-guiding-on-a-slitWhich guiders are you referring to?
AstroArt, PRISM, Audela have a specfic function optimised for guiding on a split image which can potentially guide better than PHD2. PHD2 normally just works though so if you are having problems getting PHD2 to work, I would not suggest moving to one of these at this stage.
What is the orientation of your slit? (I run mine along the Dec direction so any Dec errors due to backlash just move the star up and down the slit a bit)
Is your drift during guiding in both RA and Dec or just in Dec?If you have the green square and green cross the star has been detected ok and should be actively guiding. Also if the star moved correctly in RA and Dec during the training the mount is responding the the PHD commands.
I have seen this problem before I think. The RA (or Dec) guide corrections may have become inverted somehow (There may be a setting somewhere) so instead of correcting towards the right position it corrects in the opposite direction and the star continues to drift at an accelerating rate away from the guide position. It is connected with the meridian flip I believe. If you train and then guide on the same star does it work correctly ? Does it then not work if you move to a different star on the other side of the meridian ?
Watching how the star moves during the training is a good guide to whether the mount and settings are roughly ok. The star should move immediately in the RA direction in a series of obvious steps and then approximately back to the start position (there should be no backlash in RA if you make sure you slightly off balance the mount.) If there is backlash in Dec you will see PHD making several steps without any movement of the star (you will see a “removing backlash” message) I have lots of Dec backlash in my old eq6 but PHD still copes OK
Hello Jack,
I use PHD with my spectrographs.
(Note with PHD even when guiding properly, the star tends to move backwards and forwards across the slit because half the star is hidden when the star is slightly off the slit so it over corrects. There are guiders which work on the split image of the star on the slit but I have not used them)
You say the star wont guide on a star, the star wont stay on the slit.
Do you have the green square round the star with a green cross at the guide position?
Did the training work ok? First time you run (or if you hit shift when you start to guide) the cross is dottted yellow and the star is moved in X and Y to calibrate the guiding. (If the star does not move, there is a problem communicating with the mount and you will get an error message)
Does the star and green square stay near the guide position (centre of green cross) or does it continuously wander off?
If the star is staying around the right position but is moving around the guide position too much try guiding off the slit. Does it work ok then ?
Cheers
Robin
