rotatux

CVAstroAlign. I even used it to align native-resolution frames (of my MFT sensor) of the moon, not just videos.

However, I miss ROI selection and de-rotation from it. Thinking about writing my own tool for that tasks, or maybe patching it...

On 03/06/2019 at 13:39, rotatux said:

my Celestron MAK 127 is ~7 kg

Shame on me, I don't know what I've weighted... I re-checked this weekend and it's 3.3 kg without aperture cover. After seeing specs for the SW I had a doubt that the Celestron variant would be heavier, but that's eventually not the case.

41 minutes ago, Susaron said:

There we go with another SW130PDS shoot.

Not such a frequent subject. Pluging into the zoomed image to see the details in M106 is a delight.

As always it depends on your choices of desired targets and interpretation of "portability":

* Do you want deep-sky objects ? moon / planetary ? globulars ? A MAK would be good for moon, planetary and globulars, but rather not deep-sky (at least visually). A short-focal-ratio refractor or reflector (such as your 130PDS) would be better for deep-sky.

* On which criteria do you judge your current setup not portable enough ? Is it size : a Mak or small frac would be shorter, at the expense of luminosity; Is it weight : the 130PDS is ~4 kg and my Celestron MAK 127 is ~7 kg, so if you want lighter it must be a smaller MAK (such as 90/1250), a medium fast wide-angle refractor, or a long narrow refractor.

* You want to keep your current mount : fine, a manual alt-az is probably the lightest mount your could find, except for table-top dobson or EQ(1) mounts. Depending on your choice of instrument (i.e. if it's enough small and lighweight), you could also examine the possibility of solid tripod + small dobson (such as orion sky scanner series).

On 29/05/2019 at 22:15, happy-kat said:

@rotatux(if I have the member right) did just this a 130pds on an altaz mount for their journey in imaging.

Yes I'm often (wheather permitting) using a 130PDS on a Nexstar SLT mount, an alt-az one just to be clear. It's perfectly usable for visual, and a bit limited for astrophoto: My copy of this mount is a bit erratic and only allows 20s subs most of the time, 30s up to 40s when lucky. Other copies or mounts may be better, YMMV

You can turn the tube in the rings to place the focuser straight upside, to line up the field of view to be more natural (up/down and left/right wise) for Alt-Az and frac/cass users.

Only drawback is the vixen plate screws forbid the direct insertion of the plate in the mount: the plate must slide in the mount so one of the screws blocks the operation. I simply unscrew the front side of the plate and gently insert it (with the tube weight on my hand) before re-screwing it, trying not to change the plate alignment.

If you need more info about this config just ask (I thought a few others would be using the same, but apparently not the case).

EDIT: after reading the whole thread you (OP) appear to not have the same mount (and potential problems) as me; Your mount problably has better tracking than mine, so keep hope. However keep in mind the tube length of a 130PDS will prevent going to zenith or high altitudes, just like me, unless you use a long vixen plate and use it to offset the tube in the mount (with additional counterweights to compensate).

On 17/05/2019 at 17:50, Stub Mandrel said:

Most folks switch this off so they stay put and use flat frames instead.

My camera can't disable that auto-clean feature. And, the dust on my sensor as I checked it seems totally opaque, so I don't think flats would take care of it (or badly); "Capture dithering" in my setup would be more complicated than just a power cycle every now and then. I'm half surprised that flats work so well with others, but seeing some flats shown here I saw most dust is transparent contrary to mine (because of my smaller pixels ?).

That moving dust might also explain why I failed to make working flats so far :-/ but living well without them as you see :)

Some recently processed-during-rain images taken from february (yes I take my time :) )

First is my first acceptable horse head and flame ... at least I think so, since previous attempts didn't have enough signal. An EQ mount changes the game (coming from Alt-Az) by allowing to regularly break the 30s barrier. No darks or flats so it has some dust mites which didn't show with alt-az (because that latter moves erratically), so I should remember to regularly switch off/on the camera to let the auto-cleaning supersonic waves to move them.

Second is my first HDR, with M42 as classic subject. Came out nicely out of a relatively short exposure, and /me/ being still junior and maybe underequipped at processing.

Both captured with Olympus E-PL6 on 130PDS with SW CC and dydimium filter on Omegon EQ-300 tracking RA from a sky 50km from Paris, France (Bortle ~ 4), processed with Regim 3.4 and Fotoxx 12.01+.

What do you think ?

Exposure: 12 × 60s × 2500iso.

Exposure: 19 × 10s × 2000iso + 10 × 30s × 3200iso + 6 × 60s × 2500iso (total 14mn)

A bit deceiving: the title says "unguided" which seems to suit well with 30s, and while unguided ≠ stacked nothing in the description would forbid 30s unguided stacks, except there's that damn parenthesis to clarify and remove most hope...

On 04/03/2019 at 03:34, Vega1156 said:

I already have a Celestron Nexstar 6se

If you have it on a motorized (goto) alt-az mount, that's also fine for imaging within some constraints (and techniques to learn) -- as this thread proves. But depending on how you travel and how much space and weight you can afford this could prove too much, in which case the LX2 or self-made "barndoor trackers" are good and lightweight solutions (but limited in precision and hence focal range).

23 hours ago, Stub Mandrel said:

Have you tried a Zeiss? - it was they that invented the Sonnar configuration. This is the  135 f 3.5 wide open:

It's a nice image with regular stars on the whole field, but I can see the diffraction pattern of a closed diaphragm on bright stars... so are you sure it was wide open ? Anyway my collection only grew from trying several lenses to find an astro-correct one, and I will sell most of it ASAP but no Zeiss yet :)

My copy of the 200 (same "bokeh monster" variant as yours) is very soft at F/4, I must close nearly at F/5.6 to get decently shaped stars (esp. on borders and corners). This is why I ended getting another 200 (Olympus OM) which is fine wide open at F/4 (though it suffers another aberration).

About 135mm I've got many, 2 M42/Pentacon F/2.8 (long and short) that are both good at F/4 (the long variant is a bit better), and 2 F/3.5 from Minolta and Olympus which I barely tested but need to be closed at F/5.6 (Minolta much better). Having to close is normal I think, the shortest the focal the bigger aberrations need to be corrected by closing; Only long focals would be kept wide open, at 200/4 you can find many good ones (don't know at 200/3.5), at 135 I didn't encounter any yet (but maybe some F/2.8 from Minolta, Takumar or Pentax) -- though if you have budget there's the Samyang 135/2 which is a wonder from what I have read everywhere.

Nice start. I've got the same 200, just wondering what aperture you used, is it full open (f/4) ?

7 hours ago, Minhlead said:

Any Suggestion how to denoise for this one? I stacked with median and average

Use an algorithm which selects best samples before combining. Such as those with "sigma clipping" or "range clipping" (just a wild guess, I'm not a DSS user). They will make a *huge* difference. When you have bad data (does not seem your case), use more selective parameters.

From your number of frames, best is probably "average sigma clipping" because with a high number of frames, averaging statistically recovers more signal depth than median. Median is best with low number of frames because it converges faster (than average) to its target value, at the price of resulting precision (it would recover at most 1 bit of signal depth, when average could recover many more).

Once you use the right algorithm, only way is more data, as Ken said. Most post-processing algorithms (such as median and other linear and non linear filtering) will only smear out your image, loosing detail; Some however will help, I personnally use wavelet denoising, but I'm too young on the subject to give advice.

That Sigma APO seems to fare surprisingly good ! (I like your Orion very much)

How much did you have to close the lens' aperture ? or was it full open at 5.6 ?

Seems only the DG version is available new on the market... did you hear how it compares (optically speaking) to your D version ?

Speaking of results, here's what I could catch during my last september holidays in 3 nights — Yes I'm the multi-subject-per-night kind of man :-P.
Kind of tribute to this marvelous photon hoover
(details on separate pages in my gallery)

Night 1:

details M31

Night 2:

details M8 Laguna details M20 Trifid details M17 Omega details M16 Eagle details M33 Triangulum

Night 3:

details M45 Pleiades details Gamma Cas

Unfortunately no clear night during christmas holidays -- apart the one before I leaved

PS: sorry if layout is messy, editor/preview was a bit hard on me...

6 minutes ago, Manners2020 said:

The longer I expose the more I will have to crop because the fanning effect from stacking will be increased?

In fact I have seen that cropping also zooms in the remainging image, and so magnifies inner star trails to the point the whole image is mostly unusable. So you may be better off keeping exposure limited to a smaller value and take+process more subs.

14 minutes ago, Manners2020 said:

Mud alt = less rotation,  max exposure?

It's actually a combination of altitude and azimuth, but yes globally more alt = faster alt-az-relative rotation = less exposure. Rotation starts at a given speed low on horizon then raises to a common maximum speed (lowest possible exposures) at zenith. Azimuths East and West give the lowest rotation speed on horizon, while South and North are higher.

There's a PDF with graphs depending on your latitude somewhere in the thread... PS: I don't have it at hand, but it should be pinned somewhere as the question comes in frequently.

Hello fellow 130PDS imagers

I've processed these subs of Pleiades taken during last country holidays.
It turns out much better than my previous successful try at it, more smooth, still good colors and much more structure.

My problem is I've developped two versions of it:
* One with moderate stretching, which IMO preserves colors better (especially that Pleiades' electric blue I like so much), and still shows structure on good monitors
* Another where I pushed streching more, to ease showing on less good monitors, but it find it faded colors a bit and eventually I have mixed feeling about it.
I'm looking for others' opinion/preference/advice about which one to keep, or is more generally acceptable, as myself having good monitors at home I prefer the first one.

Thanks for looking.

2 hours ago, Adam J said:

as my focus drifts the corner stars become more egg shaped as the coma corrector only works in the far corners with perfect focus

Correct but YMMV depending on CC model and sensor size: I've seen the SkyWatcher's one being very tolerant, though with a smaller 4/3 sensor. e.g. I have used it at 2 distances separated by 19mm (factors 0.9x and 0.94x) and seen fair enough corner stars in both cases. I recognize however I don't image at the same level as most of you, I'm still a beginner in number of nights ?

2 hours ago, nm1213 said:

I was getting rotation after about 25 second exposures with the SE mount.  Sharpcap of course rotates each exposure to compensate.  However, I'd get about 30-45 minutes of stacking before I needed to crop the edges far too much to get a usable image.

Hello, 25s seems quite short, unless your were aiming at an unfavorable zone (near zenith).

However if you can cope with 30-45 minutes runs of stacking (is it what's called "video stacking"?), then I suggest you have a 30s break to manually rotate your camera in the focuser, and start another run. After a manual rotation you should be good again for 30-45min with approximately the same FoV and hence avoid cropping too much border due to rotation

PS: see "Field Rotation V3.pdf" (original here), don't read the text just look at the schemas for your latitude ; copy added to the post since original looks dead atm.

my DIY: Opened a cereal box flat, black felt stuck on inside, adhesive velcro bands on outside, et Hop ?

Goes around my 130PDS as well as MAK127.

A very nice one. I think it *is* very red actually (and confirmed by my first try at it last year).

But your stars are all white or reddish so it might be too red and need a bit of color rebalancing. Depending on the software you use, it may have the option to auto-calibrate colors based on known star colors (use it with high-depth image so ≥ 16-bit). Otherwise have a play with manual white balance, maybe after subtracting a bit of red channel.

@Manners2020 I find your Orion quite good. Comparing with unprocessed, I think you may have stripped too much of the background, hence loosing some details of the nebula you had captured. Now if this is a single sub, imagine what you will have with stacking several subs

BTW what mount was your 102 lunt on ?

Keep up trying, have good skies.

On 3/27/2018 at 14:09, smisy said:

I bought later a Celestron nexstar 8" with alt-az mount and in this year I started to take some pics about the beautifull objects on the sky. Of course at first with my mobile phone

Hello smisy and welcome to the hobby

For a beginner IMO you actually happen to start with one the most difficult configurations: long focal, high focal ratio, ridiculously small sensor, and ocular projection which magnifies again the already long focal... and of couse Alt-Az mount. So getting any images is an achievement it itself, and yours are quite decent.

Good luck and skies !

PS: your M42 looks mirrored left-right to me :-P

Your rig seems to have great potential : at first I thought "both overexposed and not stretched enough in the darks" then I reread "220s single at 400iso". Nearly 4 minutes is a great result for a wedged Alt-Az tracking, as I can't see any obvious bad tracking artefacts in your image.

That leaves you with plenty room for improvement, both for capture such as stacking many shorter exp + higher iso subs, and for processing such as non-linear stretching or black point management or color balancing. Good luck !

BTW, I find your setup is pretty unusual for A.P. -> is it a DIY wedge ? would you post some images of it somewhere ?

On 2/4/2018 at 20:15, alacant said:

Comments -especially on the colour scheme- most welcome

Your colors are lovely, especially the nebula. If I was picky I would say too strongly blue stars and missing gradation in red/orange stars, but the subject is the nebula and it has IMO nice red-orange-grey-blue variations so nothing to complain

Wish I had an occasion to get that one but weather decided otherwise and it's now probably off for me til next year.