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I did a quick calculation based on Betelgeuse subtending an effective 2 arcminutes through a minimal sized pupil, a lens which is likely defocused and has significant aberrations, mechanically scanned over an extended area of retina.
It appeared to show that one would certainly not want to stare at the SN but glances would cause no significant damage beyond very short lived after-images.
Impressive. There are several there which I would love to own, having only reproductions so far. Principia and Mechanism of the Heavens, in particular.
Somerville’s work is still well worth studying despite having been published just shy of 200 years ago.
Nick: I’m on your side. However, in my opinion it will be a courageous decision to be made and on a par with the recent re-definition of what constitutes a planet.
As space is short in the page limited Handbook, could thought be given to removing pages 117 and 118? Surely its pretty much unchanging from year to year and readily Googled? I think I used the pendulum equation once as a teenager.
Similarly, as a space saving/creating measure, could the line spacing on page 116 be changed? That might free up ~1/3rd page that could be used for some small item like expected dates of observable Earth flyby/gravity assists.
I also wonder who looks at the Bright Stars info page. Genuine question: who uses it?
BTW none of this should be taken as criticism. A huge amount of work must go into creating the Handbook and I for one am very grateful to those who put in the hours. As a result of their work I’ve already started to plan my 2025 observing year. Its good to see the Handbook evolving. Thanks to all involved!
You’re a better man than I, Gunga Din.
I also think that we could consider pruning some of the present material but didn’t mention it for fear of the likely backlash and argumentation over what could be removed and what must be kept.
I have never, ever, used the bright stars information. Similarly for those pages mentioned.
+1 for Earth fly-by and gravity assists.
Nick: undoubtedly so.
To be honest, I had never noticed but then, I’m not a planetary astronomer.
I foresee a very vigorous, not to say rancorous, debate over whether J2000 is kept in perpetuity or whether we move to J2050 within this decade.
Closely related: proper motion already affects my code which attempts to match Gaia data to historical positions. A surprisingly large number of stars have moved more than 2″ since 1950. One day I really must download the PM data too and do the job properly.
Nick: my thanks also. I am in full agreement with David on this one. 2026 edition perhaps?
Note that these two would be cost-free from a pages point of view as the charts would no longer be required.
Does “one unit of folded A4” translate into 4 pages of handbook (double sided, folded in half)? If so, two more sheets should cover Deimos,
Oberon, Umbriel, Ariel, Titania and Triton and at least couple more selected from Phobos, Phoebe, Miranda and Nereid say.Point your camera by guesswork. If your target is not in the field of view, attach a USB lead and download sighting shots to a laptop. Canon provides good software to make this possible,
Lather, rinse & repeat.
you can get to 13th mag with a Seestar now
True, but a Seestar can do much better than that. An image in the gallery show a 17th magnitude galaxy which required only 11 minutes on a SS50.
Both magnificent and profoundly sad.
They need to be brought back into productive use. I would love to use a 24″, any 24″, let alone one with such an illustrative history.
Jack,
Over the next year I will be bringing another scope into action. I already have another camera with integral FW; this has a much shorter back-focus requirement than the SX equivalent. Also purchased was a very slimline OAG pickup which takes up only 9mm of back-focus.
With judicious mix and match it should be possible to get decent guiding on both scopes and the use of the SX AO unit on one of them.
If I could figure out how to drive an SBIG OA through either MaximDL or EKOS without needing a SBIG camera it may be possible to get both systems fully equipped. OTOH, if anyone would like to purchase it … 😉
Last year I investigated changing the Dilworth’s transfer lenses to give a longer back focus but that would have been expensive, included a return trip for a delicate piece of kit to Switzerland, and would have spoiled the resolution slightly though that would have been minor as it is seeing limited in practice.
The other scope is an elderly and not very good Meade LX75 25cm Schmidt-Newtonian which will live in a ROR observatory presently under construction. That one will be fully robotic when commissioned.
Paul
Giovanni,
You have understood correctly.
So, I am using spacers to achieve focus.
I was not aware this could be an issue with some telescopes!
Regards,
JackI wish it was an issue with my telescope!
There is insufficient back focus to use an active optics unit with the current camera, off-axis guider and filter wheel. However, I have a cunning plan …
Hi Malcolm, unlike you I am still a newbie with the S50 but, like you, I plan to use it for photometry. Some of my initial research may prove useful to you.
First, the seestar_alp program is a useful extension of the iOS / Android control app. Put the S50 in station mode and control it with a real computer with a real screen, real keyboard, and real mouse, doing so from a nicely lit and warm room indoors. The program supports RA&Dec input (in J2000 and Jnow) which can be taken from a variety of sources such as Simbad as well as being typed or pasted in. It is wrotten in Python & Javascript and allegedly runs under Linux (most hosts, including RaspberryPi), Windows and MacOS. Find it at https://github.com/smart-underworld/seestar_alp
Second, AAVSO have published a set of transformation coefficients which allegedly convert native RGB measurements into (an approximation to) standard BVR photometry bands. These can be found at https://www.aavso.org/bvr-transformation-coefficients-seestar-s50
Finally, here is an image of SS Cygni taken when the VS was in outburst. I have not measure the FITS files yet.
HTH,
PaulThanks.
I never thought of switching to scenery mode, so thanks!
Dunno. Think my mind must be too highly trained Diane. (Extra points for knowing where that came from.)
Oh, woe is me.
My life is a misery.
Oh, can’t you see
That I’m at the start of a pretty big downer?This is just a self-pitying whinge, please ignore if you wish.
I am still having immense difficulties starting an imaging session with the Seestar, having just spent over an hour trying to get it set up. Part of the problem was that it took four attempts to install the latest firmware upgrade. I have no idea what I did differently this time, other than changing the firmware, for the occasion when I had a mostly successful session.
One problem, though, appears to be that the SS starts by looking at the zenith (I may be wrong) and if there is cloud around that point it fails to initialize its calibration (again I may be wrong). Although that may be an issue, waiting until the zenith is clear didn’t seem to ghelp much. Even after performing an explicit polar alignment, telling it to point to a specific object, and the telescope occasionally appears seems to be pointing in that general cloudless direction, it fails to show anything, let alone auto-focus or stack incoming images.
Perhaps I need to find a reasonably local to Cambridge and clueful SS owner whom can give me a tutorial as to how to get the damn thing working within a few minutes of taking it outside and applying power.
Note though, that time and location are both important. You need a good position and good times. So, to get accurate pointing:
1, Set the computer system clock using its “Change date and time” setting.
…Remember to activate your NTP client (operating system dependent) and configure it to use reliable low-stratum servers.
My Win10 TCS is rarely more than 20ms from reality and my Linux boxen are usually under 5ms — the one I am using now claims to be 0.214ms away from GPS time..
I use Google maps. At full zoom a position can be located to within 10m in most parts of the civilized world and in most of the US for that matter.
Right now I am sitting at 52.143392N,0.117095E and my car is parked at 52.143390 0.117336E.
The difference in latitude is .000002 degrees and at 60 nautical miles per degree, or 111.12 km, that is 22cm. The difference in longitude is 0.000241 degrees but that must be divided by cos(latitude) to convert to an angular separation. The conversion factor is 0.613254320 according to my good old Chambers 7-figure log tables. Performing the division and multiplication yields a linear separation of 44m. In reality the car is about 1m north of me but the east-west distance is actually about 18m.
Good enough for me. Note that one arcsecond is 112120 / 3600 = 31m so my co-ordinates are good to an arcsecond or better.
Hi Jack,
Do you want to use the mount to do any deep sky imaging? Both links are to Alt-Az mounts which will not be suitable for astrophotography as they will introduce field rotation, unless you use a very short exposure. Alt-Az mounts are fine for visual observing.Peter
Or fit a field rotator before the camera. Not exactly a low-cost option.
The Seestar uses 10s exposures to keep field rotation within its acceptable limits.
