Xilman

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 That said, my knowledge may be seriously out of date.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.

Also an Aspie.

There's a lot of us about.  Some estimates are around 5% of the population are somewhere on the spectrum.

1 hour ago, ONIKKINEN said:

Another solution for @pipnina  . You could mosaic images 2x2 or even 3x3 and bin aggressively. Nobody cares what shape the stars were or what sharpness issues there were if the end result is shown at 4"/pixel where it is sharp to look at anyway.

Yet another approach: assume that all the stars are distorted images of ideal point sources. All their images are then the point spread function of the optical train at the position of the star. Measure this PSF and fit a plausible (possibly spatially dependent) function to it. The fitting is an attempt to remove noise from the image.

Then deconvolve your entire image, including both fuzzy things and fairly sharp things like stars, with that PSF.  OK, this takes time, care, expertise and significant computer time but exactly the same is true of traditional AP post-processing. Note that if the PSF includes diffraction spikes from a secondary support the deconovlution will remove them too.

The process can work extremely well in practice. It was universally used on HST images before COSTAR was installed to correct for spherical aberration. I have used it myself in a few circumstances where I thought the results would be worth the additional effort.

A fair few bloated stars.  The seeing is terrible but the images are likely good enough for photometry.  Currently tracking (1956) Artek, a 16th-magnitude asteroid on the BAA-ARPS program.  It is slowly drifting westwards past TYC 1393-459-1 which is mag 11.1

1 hour ago, bosun21 said:

Depends what one regards as inexpensive. An electric focuser controllable from a laptop is over £200

I was looking at the Lakeside gear for my scopes, which is admittedly over £200. So I did a rummage around.  RVO may have something appropriate for you. The page I last looked at is https://www.rothervalleyoptics.co.uk/motorized-focusing-units/page/2/?.70001220703125&scroll=2180.466552734375 and has units somewhat cheaper.

An electronic focuser is in a similar price range to a half-way decent eyepiece or filter set.  Not cheap but hardly anything is in this hobby.

1 hour ago, Ian McCallum said:

I use the connection between my Raspberry Pi and laptop, so I've got a live FITS viewer on KStars and Okos, that allows me to see what's going on with the focus.  I still have to go out and manually focus the telescope, then come back in to see what difference it's made...

Are you able to take the laptop outside temporarily just while you focus?

I have to do much the same with the manually focused scope. Forever trotting up and down the stairs between the control room and the dome.  I really must fit an electric focus; they are relatively simple and inexpensive.

13 hours ago, Ian McCallum said:

Just looking for some input, please.  Does this image look like it's correctly focused using a Bahtinov mask for imaging?  Please bare in mind that this is from an achromatic refractor, with only a single speed manual R&P focuser.

If you can feed your images directly from the camera into a computer I heartily recommend getting hold of Bahtinov Grabber.  Available from https://www.dropbox.com/s/tp9cvni3okk1azd/Bahtinov_grabber64.exe?dl=0 and https://www.dropbox.com/s/k3tb6n32k8v78bo/Bahtinov_grabber.exe?dl=0

Works regardless of focuser type (I use it manually and with a relative motor focuser) and gets a much more precise focus than doing the same job by eye.

to me your image looks very slightly out of focus, but likely not enough to be important.

44 minutes ago, Ian McCallum said:

Try a Raspberry Pi loaded with Astroberry OS, as it supports INDI drivers for dome controls, etc.

Seconded. I am working to replacing Windoze with a tiny ARM SBC - an Odroid N2 in this case because I happen to have one lying around. It is roughly the same as a RPi 4.

The killer for me is that the dome is controlled by a Velleman board for which no INDI driver can be found. Lesvedome is the only ASCOM driver for Windoze.

If anyone knows of an INDI driver for the Velleman controller please let me know!

The Pulsar domes are well supported by INDI and Kstars/EKOS is a superb observatory control and planetarium system, so give it serious consideration.