Xilman

47 minutes ago, bomberbaz said:

Ahead of you on this one vlaiv, I moved all the pictures, video and other media from the storage on the Nvme drive onto the  8TB mechanical drive last night and that leaves me a little over 600GB free. Should cover my needs I think.

Do you take backups of that drive?

Serious question.
My files are backed up to a separate machine (a rather elderly Linux box) fitted with a ZFS 3-disk array.  Three 2TB drives give 3.6TB usable storage.  One drive hard-failed a while back and was replaced with a 4TB unit (it cost about the same as a 2TB disk) but the RAID array sailed through the episode.  The other two disks are showing faint signs of age but neither have failed yet:

pcl@ra:~$ zpool status
  pool: backup
 state: ONLINE
status: One or more devices has experienced an unrecoverable error.  An
    attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
    using 'zpool clear' or replace the device with 'zpool replace'.
   see: http://zfsonlinux.org/msg/ZFS-8000-9P
  scan: scrub repaired 0B in 0 days 13:27:01 with 0 errors on Sun Feb 12 13:51:03 2023
config:

    NAME                        STATE     READ WRITE CKSUM
    backup                      ONLINE       0     0     0
      raidz1-0                  ONLINE       0     0     0
        wwn-0x50014ee2bf658d03  ONLINE       0     0     0
        wwn-0x5000c500c0fc45a7  ONLINE       0     0     3
        wwn-0x5000c500c0d65bf2  ONLINE       0     0     2

errors: No known data errors
pcl@ra:~$ df -h /var/lib/backuppc
Filesystem      Size  Used Avail Use% Mounted on
backup          3.6T  1.2T  2.4T  33% /var/lib/backuppc

I will replace them when I return to Cambridge.

My experience is that SATA SSD are markedly faster than SATA HDD. This holds even when each drive is plugged into identically the same cable and SATA port.

One big difference is latency. If the sector you want to read or write is on the opposite side of the platter from the R/W head, you have to wait for half a rotation period (over 100 microseconds) for anything to happen to a HDD. Latency is hundreds of times smaller on a SSD.

Over the decades a great deal of effort has gone into hiding this latency by intelligent reordering of sector layout and disk operations, caching (originally just in system RAM but now also on-HDD) but it can not be eliminated entirely.

On 18/02/2023 at 22:17, Xilman said:

 Might give it a try now that I know of its existence but don't expect to have much success ...

Here is a teaser.  Rather more later, I hope, when I have finished collecting data and processed the results properly.

On the left is my crude attempt.  On the right is the DSS2 image as displayed by Aladin Lite. Note my camera is rotated by about 12 degrees.

This is the magnificently named (229762) Gǃkúnǁʼhòmdímà.  It is a Scattered-Disk Object, meaning it orbits the sun in an eccentric (e=0.4843) and highly inclined (i=23.378 degrees) orbit.At the time of observations (2023-02-23) it was 40.95 AU from the earth and magnitude 19.8.  The image shows a very small trail of the SDO, which may be compared with the circular appearance of stars of similar brightness.

Technical details: 0.4m Dilworth, unfiltered SX814 CCD camera. 2790s exposure in 93 subs of 30s each.

(No I can't pronounce the name, despite having heard it spoken.  It will always be (229762) to me.)

12 hours ago, Paul M said:

Fascinating subject Paul, we've discussed it a few times in the past and I just happened to to look at some of your other images of far-flung Solar System objects on your web pages a couple of days ago.

I hope to capture a few before spring gives way to summer.

If you check the BAA Handbook you will find a few close to or somewhat past opposition (so visible in the evening sky) and at a fairly northern declination.Over a year there appear to be 12 which reach mag 20.0 or brighter, which should be within range of a single night's observation with a 20cm or larger. This estimate is based on the facts that my 40cm has four times the collecting area and took 85 minutes to reach mag 20.3 with ease.

Good luck with your project and please display your achievements here.

Two possibilities immediately come to mind.

One is to rename "Planetary" to "Solar System Bodies Other Than Sun or Moon" which encompasses the topic very nicely but may seem a little long-winded. There may be better phrasing.

The other is to create "Small Solar System Bodies" and leave it to the good sense (if any!) of the posters.

I favour the latter.

Paul

To get things started, here is an image of (20000) Varuna taken on 2023-02-20. 177x30-second subs were taken with an unfiltered SX814 camera attached to a 40cm Dilworth. The subs were stacked on the stars because the KBO moved less than 5 arcsec during the observation. (Incidentally, that's an advantage of imaging TBOs because they move so slowly, even at opposition.) The position (08:42:04, +27:15:24), motion (3 arcsec / hour), predicted magnitude (V=20.3), distance (44.1 AU) , and so forth obtained from the MPC facility at https://minorplanetcenter.net/iau/MPEph/MPEph.html

Incidentally, most of the objects of comparable brightness to (20000) Varuna are background galaxies and not stars. Some can be seen to be elongated and/or diffuse in appearance.

Starting this thread for the posting of images and discussion of trans-Neptunian objects such as plutinos, Kuiper Belt Objects (KBOs), Scattered Disc Objects (SDOs), Cubewanos and other such members of the zoo. A whole bunch are within range of amateur imaging and one, Pluto, can be see visually in, say, a 30cm reflector. The BAA Handbook contains a list of the brightest TNOs each year.

There appears not to be a sub-forum for these beasties and "planetary" appears to be the least inappropriate option. If the powers-that-be would like to create one and move this thread there ...

Thanks, I will check this again.

I am a confirmed CCD fan for the reasons you give, though darks are needed as well as flats and biases if you want accurately measurable images. All can be taken during daylight or cloudy nights and a library of calibration images lasts for months, IME anyway. Dark response is linear and so dark frames can be scaled to sundry exposure times.

The SX cameras have 16-bit dynamic range, rather better than the CMOS versions with which I am familiar. That said, my knowledge may be seriously out of date.

Unless you live on a mountain top (I don't know Dorset very well but I believe it is fairly low-lying 😉) 0.92"/pix is a good match for the Nyquist criterion for your seeing.

On 15/02/2023 at 11:08, DaveS said:

However, if the 694 at ~0.46"/px is silly, then the 533 at ~0.38 "/px is downright ludicrous. I could bin it at 2x2, but that would be 0.76"/px, at which point I might as well use the G3 16200 at bin 1 and crop.

FWIW, I use a SX 814 Pro, but Terry Platt very kindly loaned me one of his personal 694s while my camera was being repaired --- I am familiar with the 694, in other words.

To the point: the pixel size on my 2614mm focal length scope with the 814 is 0.29"/pixel which might be thought ludicrous. However, the diffraction limit is 0.31" so it is actually a good fit in certain circumstances. I generally bin 2x2, so getting 0.58" per pixel and the seeing is generally in the range 2-3". Still oversampling, you may think. However it has advantages. For a start, the response is linear right up to a few counts short of 64K because a binned count of 64K spread over 4 pixels is only 16K per pixel, well within the linear range. Unbinned, linearity tends to drop off at around 50K. The extra 20% range is well worth it in my opinion.

Secondly, the Nyquist criterion states that at least 2 samples per feature must be taken for it to be detected. Twice 0.58" is a reasonable match for seeing-limited imaging.

Third: seeing need not be a limiting factor. Lucky imaging and speckle imaging monitor the instantaneous condition of the atmosphere, not its time-average. I have used 1ms through 10ms unbinned exposures to freeze the detail of close double stars, the moon and bright planets.

Fourth, and this is closely related to the second, deconvolution in software is also Nyquist limited. If you have a well-sampled point spread function, the image of a bright star for instance, it is amazing what maximum entropy, RL, CLEAN, etc, can do.

Fifth, if you want to do photometry it is generally better to spread the light of a star or asteroid over a number of pixels, thereby averaging out pixel-to-pixel variations in sensitivity as the image moves over the sensor.

Don't discount small pixel sizes, in other words.

Paul

Advice please.  Are asteroids, TNOs, KBOs, SDOs and other such TLAs "planetary" objects for the purpose of uploading images of them to SGL?

It is far from obvious to me where they should live.

Much the same could be said for planetary satellites like Leda, Albiorix, Caliban, and Nereid but at least they orbit honest-to-$DEITY planets.

I ask because I have almost run out of planetary satellites within range of my kit (Phobos and Mimas may be possible) and have turned to other similar objects in solar orbit.  The TNO (20000) Varuna is coming along nicely tonight.

14 minutes ago, Xilman said:

It will make a difference but I guess only a little one.  I can (and will find out) but ...

My observations from 2022-10-31.0 show AE And at V=17.22 ± 0.05 and AF And at V=16.39 ± 0.02  so a change, but not very much.

Incidentally, close inspection (and I mean close, I have only just noticed it) the stars show a slight colour gradient, being generally bluer at the top and redder at the bottom.

No idea what may be the cause, but it may be atmospheric dispersion or imperfect stacking of the subs.

It will make a difference but I guess only a little one.  I can (and will find out) but these are enormous blue supergiant stars and are extremely luminous --- somewhere between 50K and 500K times as bright as the Sun.  As such, they take a long time (weeks or months or more) to change in brightness other than in exceptional circumstances. The first is when they go supernova, which they haven't yet but will inevitably do so quite soon - in the next few million years. The second is if they are eclipsed or gravitationally lensed by another fainter star. There are no reports in the literature but I may have, just, picked up an eclipse though much more careful analysis is required.

Since I have been following them, AE And has faded by about a magnitude, which means it is now only 40% of its earlier luminosity.

Incidentally, please measure objects in your images and submit your results. You can certainly do valuable scientific research while also producing attractive images. If you, or anyone else for that matter, would like assistance I would be happy to oblige. As you have demonstrated, you can produce measurable images of individual stars in nearby external galaxies such as M31 and M33. Stars in our galaxy are easy by comparison!

First thing I always look for in images of M31 is the clarity of the stars. The first star is generally AE And, which is a LBV (luminous blue variable) star in the galaxy. It has been on my observing program for years and so can spot the region at a glance. Another LBV, AF And is also on the program.

By this metric the lower image is superior but both are good.

Here are the locations of the two variables on your image, with a zoom factor of 4 so that individual pixels can be seen. Note that AE And is markedly fainter than AF And, which is in line with my recent measurements. AE And was at V=17.52 and AF And at V=16.14 on 2023-01-24.0.  I guess your limiting magnitude is around 18.0 to 18.2.

AE And:              AF And:   

Here is an amateur image of 3C273 and its jet https://britastro.org/observations/observation.php?id=20220207_155425_db3009e6821ce52f which shows the size and brightness differential rather nicely. Note 15 minutes exposure on a 0.5m telescope. You (Paul M) will need at least an hour.

My image (10 minutes on a 0.4m) of the jet of M87 is here https://britastro.org/observations/observation.php?id=20220401_141632_b78b6439f53880d9

20 minutes ago, Paul M said:

You'll have to remind/educate me. I don't recall that particular adventure!

Seconded. Time to have a chat with DuckDuckGo ...

Ah, here we are: https://en.wikipedia.org/wiki/Cosmic_Horseshoe

With a quoted B magnitude of 20.3 I expect it to be not entirely trivial to image.  Might give it a try now that I know of its existence but don't expect to have much success and certainly not until the dust has cleared out of the sky around here. When Orion's belt is a difficult naked eye object I don't even bother to open up the observatory.

Added in edit: a rummage around in Simbad and Aladin suggests that it may not be completely out of the question. A few hours unfiltered exposure should be enough. I have reached fainter than mag 22.0 on stellar objects before now. It emphatically will not be a pretty picture!

Thanks for making the suggestion.

Looks good to me, and congratulations on picking up two asteroids. Getting one serendipitously is fairly uncommon.

Remember that the jet is not very long and much fainter than the quasar's core. You may well have captured it but have not yet enlarged the image enough and/or performed some rather vigorous contrast enhancement. It's certainly possible to image with a 25cm scope but not entirely trivial.

If you are into relativistic jets, you may wish to have a go at M87 later this year. It is somewhat easier than 3C273 in my experience.

Please keep trying. Not many people seek out things like this because they don't yield pretty pictures, but I like the challenge more than the aesthetics.

One thing to bear in mind: the planets have relatively small angular sizes and so you need a magnification high enough to see them as anything but very small spots. To put things into perspective, Jupiter is at best 1/40 of the size of the Moon when viewed through a telescope, and Mars is significantly smaller. This may help you judge what you can expect to see through your scope.

Don't over do the magnification, though, or you will just end up with a blurry unfocusable splodge.

Back in the days when I had a 18" Dob built out of wood, so rather heavy, I had a friend build a trolley out of box-section steel and four heavy duty caster wheels. It had wheelbarrow-style handles at each end.  Cost me well under £100 but that was around 35 years ago.

You may wish to investigate something similar.

47 minutes ago, Optic Nerve said:

 its just a bit of a blow to my ego that I am basically being outsmarted by a mirror

You don't have to be a newbie to be outsmarted by a mirror, believe me.

I first used a Newtonian in 1975. I still loathe having to collimate them, especially bobbing up and down from one end of the scope to the other to see what difference twiddling a screw at the back of the primary has made and then trying to remember which screw and in which direction and by how much.

I really don't know how much hassle Tezz wants, nor how many friends he has willing to lug delicate equipment around at night, both before and after observing sessions. Especially, after, which could well be after most normal people's bed time.

With that in mind, I would definitely consider subscribing to an internet-connected robotic telescope. Robots do >90% of the donkey work and there are people who have the knowledge of how to do the rest. The scopes tend to be located in clearer darker skies and (something many do not really think about) closer to the equator than the UK. The last means you can observe much more of the sky.

A search on "remote telescope", "robotic telescope", "internet telescope" will dig up a number of providers for you to check out. A good rummage around will turn up dozens, catering for all interests, experience levels and budgets. By and large, £4K (or the equivalent €4500 or $4500) will get you really quite a lot, including much larger apertures (up to at least 0.5m), multiple filter sets, high sensitive cameras, rock solid mounts and tracking, etc.

The first term gave https://telescope.live/home and several others on the first page of results.

The second gave https://www.virtualtelescope.eu/ .

The third gave https://www.slooh.com/everyone and others.

I know personally several people who use SLOOH, some of them BAA members who use it as part of their research programs. The SLOOH north telescopes are on Tenerife, just a short ferry ride from here, and the southern ones are in Chile. Both much closer to the equator and both under much better skies than the UK.

Disclaimer: I do not use a robotic telescope, other than one which is sited next to my observatory in La Palma. That scope is owned and run by a guy who lives in Cheshire. He lets me use it occasionally when I am in the UK and can not access my own facility. I have no business interest in any of the outfits mentioned above.

Paul

As far as I know, this is the very first image of a comet I have ever taken. It is of the famous 29P Schwassman-Wachmann which undergoes outbursts every so often. Very bight nucleus and extensive coma.

930 seconds unfiltered through a 0.4m Dilworth. Taken 2023 Jan 14 - 23:30 From Tacande Observatory.

7 hours ago, Mr Spock said:

Perhaps a thread in the non astro Lounge would be best suited to an ASD discussion 

You have more power, being a mod, than I.

Make it so.