pipnina

11 minutes ago, ONIKKINEN said:

Not familiar enough with the 183 to say if its something that can do without dithering, but as mentioned above the newest very clean IMX571/533 cameras can work without dithering, provided that the polar alignment is competently done, darks are well matched (and maybe that there is no significant cone error).

For my 571, the hot pixels are there but get removed by the default settings in pixinsight. I do dither though on every 3rd sub.

I also found that for my much noisier Nikon D3200 which had super bright hot pixels, that the hot pixels would overpower the signal even when dithering and the hot pixels would trail all over my images. However the ultimate savior for me was the Sigma-clipping stacking method. It does a phenominal job of removing hot pixels if you dither your subs.

Here is the rejection map for a 1.5 hour stack of 17 second exposures taken on my google Pixel6 on the main camera, when using sigma clipping in pixinsight. My goodness!

And the final stack, once I finished processing... Those hot pixels are gone!

Ok, the image isn't exactly "clean", but we are dealing with a very tiny and poor quality sensor, plus optics that have a very complicated distortion and abberation pattern which makes it impossible to work with in a desirable way for astro. But if sigma clipping can make a phone produce an image this good and remove all that gunk from it, it should work just as beautifully on a much higher quality astrocam!

The colour in those stars is gorgeous!

I agree it looks like the IR light on the phone reflecting off of the eyepiece. Like Elp says you can probably stick something over the IR bulb (use online diagrams to find it, it's quite well hidden from the eye on my phone).

I'd say you should experiment with your current gear and consider upgrading only when you feel confident that it's the right next step, after you've tried things like stacking phone videos on planets etc.

Good luck!

The telescope has made it home!

Es said he cleaned the lenses, identified the middle element as a "fluor crown" and said it had a slight mistiness to it, but he has attempted to clean it up. He also epoxied the focuser to the tube so it should now be nice and rigidly attached, unlike when i sent it to him.

Sadly the weather tonight is poor and the forecast doesn't show much hope either, but I hope to test it soon!

I actually thought he was underselling himself a bit when he gave me the bill, but as long as he's happily compensated and i haven't broken my bank all is well I suppose.

Fingers crossed!

I don't know about eyepieces, but when i took up the option for lens thinning years ago my vision was plagued by chromatic abberation even slightly off center. Never taken that option since despite my Professor Farnsworth thick lenses.

I love the redder tone in the bottom one!

I feel like if you could somehow combine the rich orange in the bottom with the slightly deeper blue of the top image it you'd have the best of both!

Amazing!

On 07/02/2023 at 14:10, fwm891 said:

I'm in the process of getting an Orion Optics (UK) VX10 with 1/10th wave optics which I will be using with (at present) a couple of cameras: AA 26C and an ASi585MC. I have a Nikon 800E and D5100 although I'm not planning on using these regularly with the 10 inch.

My question:

I currently use a Baader MPCC Mk III coma corrector with an Altair 102ED Ascent refractor, which after tweaking the spacing gives me quite reasonable stars to the corners of the 26C and I will probably continue using this on the VX10. From playing with a FoV simulator (https://12dstring.me.uk/fovcalc.php#) I'd like to add a reducer/flattener into the mix but really unsure about which to go with. How much reduction: probably around 0.75x - 0.8x reduction.

Anyone here using a similar scope with reducers? would love to hear the goods and not so goods about them.

Thanks Francis

I realised i forgot to link the corrector I found before:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p14460_Starizona-Nexus-0-75x-Newtonian-Focal-Reducer---Coma-Corrector.html

As I stated... it is not cheap! And only advertises correction to slightly shy of APS-C format (28mm circle, compared to diagonal of most APS-C sensors around 31mm). The example images look good, but aren't very high res and look like they might use some starless processing? hard to say.

This is so far the only coma corrector to offer more than just a little bit (i.e. more than 0.95x) reduction.

Seems I've unintentionally paper bombed his workshop 😅 

I used (per recommendation of a local store) printer paper scrunched up to cushion the bottom of the box, and the other end was cushioned with bubble wrap... And I forgot to mark which end was which! Plus, my botch job at affixing the focuser to the tube has failed on him as he lifted it from the box... Oh dear. I have apologised but he did say it made him laugh so there's that.

On the plus side early impressions of the optics are promising!

The scope is now in the hands of Es, awaiting prognosis!

I had to find a new post office as the one most local to me has closed down as if jan 1st, in the end postage via parcel force 48 came to £72!

DHL didn't charge that much, but it's Es' preferred courier so I figure he trusts them for a reason (well he said Post office, but I think royal mail doesn't deal with items this size, leaving PF as the only other option). But I also don't know if DHL was told the sale value of the parcel when it was sent to me.

Maybe I could have sent it cheaper if I undervalued the parcel (I used the value I bought the scope for) but even though glass isn't insured, I'd be devastated if the parcel was lost entirely while undervalued by the courier.

At any rate, fingers crossed!

1 hour ago, saac said:

I can't comment on the situation in Dartmoor as I don't have any real knowledge of the area. In Scotland however the problem is not with the estates or what they do with their land re population of deer.  These populations are managed. The problem as I have seen it over the past 30 years or so is simply the growth in human footfall  facilitated by tourism.  An overly romanticised PR effort on behalf of Scottish Tourist Board/Visit Scotland aided and abetted by the movie industry (how many times must the Old Man of Storr feature)  has resulted in trashing of the countryside.  Outsized vehicles blocking single lane roads, far too many feet trampling on areas of special scientific interest, the Cairngorm plateau damaged beyond repair, human waste scattered on mountain and woodland trails and the detritus of human activity left at campsite and wild places (whole tents).  This is nothing short of "rape" of the land I use that word with caution but it is.  Sorry, but this is not deer or managed estates that are causing this , this is simply people and far too many of them in a small area.  It's time we ramp up tourist tax as is being considered in the major cities such as Edinburgh and even reconsidered controlled access by permit to the Scottish mountains. John Muir would be appalled to see how we are treating our wilderness now. 

Jim 

Sadly I think it's true. While I wish this not to be misconstrued, I do believe humans have managed to violently overpopulate and we would have been better off ecologically plateauing about 5BN people ago, which lines up roughly with what our planet could have provided for us without the use of fertilisers (originally bird poo scooped from islands and mined in a manner most irresponsible which would have led to the famine of billions if not for the discovery of synthesized fertilisers prior to WW1).

We consume food in volumes that could never exist via "natural" means, much of which is grown on land claimed from ecosystems that are destroyed for farming, and then is fed to livestock (98KG of grain turns into 1KG of beef).

We package everything, and make so many of our daily materials out of stuff we cannot dispose of. Plastic recycling is little more than a fantasy as almost all plastics go un-recycled and end up burned or in landfill eventually (many poor nations are effectively poisoned as richer nations pay them to take their plastic waste, those nations then have little choice but to burn it, which releases extremely toxic chemicals). Even PLA, which is made of corn starches, cannot be biodegraded as advertised in nature, it requires enzymes that are artificial and high temperatures. Plus, every PLA on the market is packed with additives or is even an "alloy" with other plastics which mean recycling and complete composting cannot happen in many cases, leaving us with incineration as the only option for proper disposal.

Air travel (which still uses lead additive fuel) allows us to visit places en masse, and ruin them just as fast. I would very much like to travel and meet my distant friends, but it's hard to compare my feelings and desire to see other lands to the damage I would/could cause in collaboration with everyone else doing the same.

I think this is only the tip of the iceberg for what we do to this planet, and ultimately ourselves. Plunder now, regret... Sometime in the future.

I have developed a lot of anxiety around my own environmental impact. Near enough everything I buy or throw away gives me this inkling of guilt, but it's not like I can just... Stop living? If I didn't buy things that would eventually turn into waste, I'd just sit here like a lemon for my whole life, never enjoying anything, as all my hobbies cause some kind of unspeakable damage, and I'm not much one for reading and gardening is something you can only do so much of in a day, if you have a garden.

I apologize for being so morbid but it's what weighs on me whenever ecological / environmental happenings get discussed 😕

I have only done research on this myself, but reducer coma correctors seem extremely rare, and when you find one, it's expensive! (Think £500+!)

I found them with 0.75x mag, and they all claimed to be suitable up to APSC, but then the 4element GPU corrector claimed to be full frame suitable, and I don't think it was based on my own experience.

From what I understand, parabolic mirrors are great if you plan on using them plain with eyepieces etc, but awful if you want to correct the peripheral field as well. This is because coma correctors end up creating some spherical abberation (like the Baader) at the center as a result of the parabolic mirror being perfectly corrected for sphere already. But if you paired the Baader mpcc with a hyperbolic mirror (somewhere around k=1.22 according to people on cloudy nights) the center would be corrected for sphere as well as reasonably corrected at the edges.

I can see if I can find the correctors when I get home and drop you the links. For now though I might say it's a bit "untested" as I struggled to find high Res example images, let alone raw subs!

Best of luck with your new kit!

I actually sold my sigma 105 f2.8 macro last year after I got rid of my DSLR. It did handle quite well but star shapes weren't exactly ideal at the corners, and that was on an aps-c sensor, and the lens is supposed to be full frame suitable.

It was very good at normal photographs though, I definitely got my money's worth from it.

This capture is very nice too, beats a lot of stuff I captured with mine for sure. Shows what happens when it ends up in the hands of someone capable ha.

On 02/02/2023 at 22:22, Shaun_Astro said:

I did just buy this lens (used example) for my star adventurer. I did look up sigma 105mm on Astrobin, but I see they all use the 105mm f/1.8 ART, which is 3X the price! 

Still should yield better results than my Canon 75-300mm, but this is miles off the Rokinon/Samyang 135mm. Might see if I can return it and put the ££ towards that, a lot of the stars seem quite misshapen around the edges. Have you tried star tools and the star shrink? Great picture for the exposure time though, just a lot more field curvature than I had expected.

I looked at the art lenses, as well as the Zeiss lineup when looking for imaging lenses in the 1-200mm focal length range... Sadly while all very well corrected for distortion and chroma, ALL of the fast lenses have insanely high vignetting (most of the f1.4 lenses are only 30% illuminated at best by the corner of a full frame sensor) and the MTF curve is very dodgy. Plus they cost as much as or more than a redcat51 or askar ACL 200. 

I'm sure I'd adore those lenses for regular photography, but my mind does so much more pixel peeping with astro!

7 minutes ago, scotty1 said:

Hi Mike

Yes I've been looking at Cometwatch http://aerith.net/comet/weekly/current.html and it says  magnitude being about 10. On Stellarium it's listed as 16. 

Took a few shots earlier at 300mm , but the moon and my budget setup (DSLR and zoom lens) maybe asking a bit much.

This might explain why my dad and I were struggling to see it, stellarium on mobile has it as mag 5.8, I was struggling to see the comet but mag 8, 9 stars were easy in my 10x50s tonight.

2 hours ago, mrflib said:

Hello fellow space dudes

 

I am getting some odd refections on my subs when I try to image M45. I was at a dark site and in the end had to switch targets - I did not get these same reflections on M31 or M51. I only tried LUM and RED filters on M45 before switching targets (dark sky time, can't waste it!) and the same refecltion was on both filters. I've never imaged M45 and I've not seen these reflections before.

I've made an album linked below. All targets were taken on the same night.

 

SINGLE FRAME STF STRECHED SUBS HERE

 

I am running:

Sharpstar 94EDPH > 0.8x Matched Sharpstar Reducer > ZWO OAG-L >> ZWO 7x2 Filter Wheel >  ZWO 2600MM

I use Antlia LRGB V-series Pro filters (unmounted, black edge, 36mm) and Antlia 3nm 36mm Ha SII OIII (unmounted, black edge, 36mm).

https://www.365astro...-36mm-unmounted

https://www.365astro...-36mm-unmounted

https://www.365astro...-36mm-unmounted

https://www.365astro...-36mm-unmounted

 

I do have some shadow from the OAG but flats take that out - bottom 2 images in the album show them.

Looking at a wider frame image of M45 on astrobin I can't see any bright stars out of frame that might be causing this? There was no moon.

https://www.astrobin.../full/d8a4jn/0/

I can't see any scratches or marks on any of the spacers / image train. The 94EDPH is flocked with black fabric inside the tube. The OAG is adjusted on the tilt plate for a flat field and black tape is around the outside edge of the whole OAG to stop light.

Any ideas!

 

(I have posted this on CN too)

 

Also, you aren't following the topic - heads up

The only idea I have is to set the telescope up during a cloudy night, point it at a bright torch of some sort (could make a pinhole in a foil sheet to simulate a star maybe), and move the bright light source around the field of view of the scope, even out of field, and see if the reflection pops up.

When you find it, be meticulous in working out where it's coming from. Remove the corrector and see if it's still there, then try the filter wheel, oag, even take the cam off entirely and see if it's also there in an eyepiece.

Looking at where the focal point of that curve would land, way off screen, the only bright object in that area is mars... Does it show up in the field if mars is near by? It's brighter than any star by a long margin so if anything can cause a reflection in an otherwise dark sky that might be it.

2 minutes ago, vlaiv said:

That is interesting. I would have thought that at F/4 with shorter tube - it is lighter scope.

I balance my RC8" with 10Kg counterweights with no problem - I even add 1Kg at the front because scope is back heavy.

That OTA weights 8.5Kg according to FLO.

I think that some of it has to do with how close scope is mounted to the center of mass. RC8" has dove tail attached directly to OTA - so it is sort of "low profile".

The tipping point was probably that my 50mm/f4 finder was mounted on a 30cm dovetail on the top of the tube rings, about as far away as it could possibly be. This was to get it off of the tube itself as I suspected it was causing flexure when guiding. Plus I had a losmandy dovetail on the main scope which was heavier and a big flexible dew shield on the front of the scope to try and cut out some of those off-axis reflections.

quite possible I simply added more accessories to mine / further away etc. The newt wasn't far off balance though, a piece of string with my star adventurer's 1kg weight on it hanging off the counterweight bar mostly fixed it.

20 minutes ago, vlaiv said:

Look at it this way.

Specs for EQ5 mount are:

"Payload Capacity: Approx 6.5kg for imaging and 9kg for visual"

(according the FLO website specs)

8" PDS OTA from SkyWatcher is 8.8Kg.

Add few accessories - like eyepiece, finder scope and such and you are already over 9Kg limit for visual. You can never reach recommended limit for astrophotography with that scope as scope itself is already heavier (and you'll want to add DSLR or camera, adapters, guide scope and guide camera and so on).

I personally don't like newtonians on EQ mount for visual. This is because you either have to be very bendy to get into right position as eyepiece orientation moves as OTA slews around the sky - or you have to rotate OTA to have eye piece at comfortable position. This means undoing rings - rotating OTA - fastening rings back - every time you change target and slew considerable distance. 6" Ota is much more manageable for this than 8".

EQ5 is light weight mount. I know it looks sturdy compared to something like EQ2 or EQ3, but in reality it is just light weight mount - almost being lightest weight mount worth using. (EQ3 is good for some grab and go visual and imaging with just camera and lens).

For large OTA that is susceptible to wind - you want massive mount. Reality is - I would not use 8" F/5 even on HEQ5 - I'd put it on EQ6 class mount.

I have Heq5 and I have 8" scope on it - but it is RC - and that is shorter and more compact than 8" F/5 scope - and I consider that to be on limit. I've put 8" f/6 on HEQ5 and imaged with it - once (that was enough to show what's what).

 

Both my 8" F4 newt and 130mm f6.6 triplet are impossible to balance on my HEQ5. the 10KG of counterweights is simply not enough for either of them.

I still get sub-arcsecond guiding (typical between 0.5-0.8RMS total) with both, but the refractor is definitely more stable with fewer wobbles, probably on account of having a lesser wind profile.

I have wanted a mount upgrade for a while, but the market seems to be moving a fair bit at the moment and the choice is not as clear cut as i think it was when I bought the HEQ5 in 2017, many more options in the £1500-4000 price range than just stepping up to a higher tier skywatcher mount.

On 13/01/2023 at 20:43, saac said:

This is exactly the problem, you have hit the nail squarely on the head.  While in Scotland we benefit from the "right to roam" legislation, over the past 10 years or so it has been self evident that we are suffering from over tourism.  We are a small country (and I include the whole of the UK in that ), it is difficult for the environment to survive against the increase in human traffic.  Advertising of our remote and wild places on social media, TV, movies etc have all contributed to increasing footfall; how long is it going to take for us to realise just how fragile these places are.  I do have sympathy for the landowner here. 

Jim  

I can't remember where, so I don't know how accurately my memory serves, but I think I read/heard that areas in the lake district do their absolute best to keep tourists on specific paths so the sheer volume of people doesn't destroy the very thing they've come to see.

We closed off stone henge with a fence because people kept vandalising it

We can no longer enter the prehistoric caves with the paintings in france (discovered during WW2) because the presence of moisture from human breath and artificial lighting caused plants/moss etc to grow on the walls, slowly destroying the paintings so that we could view them. So they built a replica "next door" and closed off the original to everyone except scientists.

Look at any major tourist / package holiday city before and after the rise of the aeroplane, the effect of the tourism industry is almost always unintentionally destructive.

Best we can do is keep our own impact to a minimum when we visit, and for affected areas to impose limits and controls to preserve what makes them special.

Most of these places only exist as they are once!

I can't attest to photoshop's needs, but as a Pixinsight user I find RAM quantity, drive speed and multi-core CPU performance to be very important.

Some stacks I've done (where about 800 24MP subs were used) have literally consumed all 96GB of ram in my system and then started to eat into my 50GB swap on my SSD too. But Pixinsight's process is insanely poor performance compared to alternative stackers. It also takes up a lot of disk bandwidth and IOPS (in-out operations per second) so my SATA3 SSD only just keeps up.

I use a Ryzen 5800X but given as the 5950x is faster in every way and also about the price I paid for my 5800x at launch these days... That might be the CPU to get as the new gen 7000s are a bit pricy for a slightly underwhelming gain I hear.

3 minutes ago, wulfrun said:

The AE-1 has a centre-weighted metering system, in the daytime photos you have a lot of bright sky and I'd bet that's fooled it. In the days of film cameras, modern evaluative systems didn’t exist and you'd learn to think about when to accept its readings and when to "interpret" them (i.e. override and correct it!).

So if I wanted the ground to be properly exposed, I should get a meter reading with the center of the frame pointed at the ground, then frame my shot? Works for me if that's the case, I was probably exposing for the sky.

5 minutes ago, Paul M said:

I did once have a roll of hypered tech pan in my parents freezer.

When I found it again years later I couldn't remember whether I'd even exposed it!

What I remember is that it's a fine grain,  B&W film developed for technical photography that lent itself to hypering. Thereby making it very useful for long exposure astro imaging. 

"Pushing" was/is a standard darkroom technique whereby the film is developed slightly longer than the prescribed time to increase image density on the film. Easy to overcook it though. Bit of a dark art. And if film processing goes wrong then the whole imaging session is lost. 

To say that digital cameras and image processing were a revolution in astrophotography is a huge understatement. 

That Ilford film I linked will likely give you better results. Faster film generally means courser grain but on star fields you probably won't be too worried. 

It would be interesting to see what results can be a achieved with a film camera that is guided on a modern mount. Because as guided mounts arrived, film was just about ending. Hand guiding was perhaps the most dedicated of dark arts in a niche corner of a niche hobby.

I guess I can only give it a shot and see what happens! My first thought was that I'd try another Rollei-IR film shot but stick it on my guided HEQ5 and do some half hour to hour+ shots and see if they come out better. I think I'll try the Illford film though as you suggest as you have prior experience. What sort of exposure times might one manage there before over-exposing it? My skies are around mag 3-4.5 NELM depending on where I'm facing.

Funny you should mention a modern mount and a film camera together, as that's what inspired me in the first place to give this a go: https://petapixel.com/2020/04/25/how-i-photograph-the-milky-way-with-medium-format-film/

This shot in particular!

18 hours ago, Paul M said:

Maybe not the best film for astro images. I'd have gone for something much faster:

https://www.jessops.com/p/ilford/delta-3200-professional-35mm-36-exposure-black-and-white-film-18426

Who's processing/printing the film. Getting the exposure is only half the job, as it is with modern digital imaging. Astro benefits from custom developing and printing. Knowledge of the film's characteristics helps to decide whether it can be "pushed" in the developing stage. 

I used to have an enlarger but really found printing form negatives to be hard work. So preferred transparencies. 

One thing I remember from those days is Reciprocity Failure. Photographic emulsion does not have a linear exposure response and it's a game of diminishing returns on long exposures. That's why hardcore Astro photographers used to "hyper" their film such as Tech Pan 2415, to overcome reciprocity failure.

Whatever the frustrations of modern imaging are, they pale into insignificance when compared with film!!

 

I've done some reading about this Tech Pan but I'm not quite sure what it does differently to normal film, or if the benefit for astro is in the development and processing.

Some local person is developing it, through a local shop dedicated to film photography.

I presume that "pushing" helps to increase the brightness of the film, but is that just exaggerating the contrast already present in the film (can't boost the brightness of something that already has no signal) or is it bringing out chemical differences that otherwise would not affect the transparency?

I'll have a look at this illford film and see if I can try it out on my next attempts, I'll also speak to the guy in the shop as he may stock it and have advice for shooting too

Thanks!

A few months ago I figured I'd give my dad's Canon Æ-1 Program a dust off after I found out about a film photography shop in my town center. I looked at the data sheets for a few kinds of film and seemingly only Fujifilm Velvia (colour, the same film used to capture the famous windows xp desktop background) and Rollei Infrarot (Black and white) have spectral response at the hydrogen alpha emission line. I figured I'd pick up the rollei.

I am definitely grateful that the cameras and lenses of the day had good focusing marks, or i would not have been able to focus on stars at all without hoping a bahtinov mask would be bright enough. The focusing prism definitely only works in daylight conditions and when hard edges are present...

I stuck it on my star adventurer mount and took some photos. In my notes I took them of Andromeda, Cassiopeia and Cygnus. Either at 35mm or 105mm (my dad used a vivitar 35-105mm lens, so I opted to only use the extremes).

Sadly the best I got from it was this... Not exactly what I hoped... Weirdly enough even normal photographs I took came out very poor, despite using the camera's inbuilt metering system (and setting the ISO on the camera body to the 400 declared on the film can). Maybe some film photographers here might know what's going on, but I am going to mention it to the guy in the store because he seems very knowledgeable (has in-repair cameras all over the store!) and could point me towards user error, dodgy processing, bad scans etc.

So here we go: 6 minutes pointed at Cassiopeia yielded me this. Oh dear. And this was the best one!

It doesn't help that the scans I got back were in jpeg format, and the scanner is not bias frame calibrated (those noise bands!)

This was clearly one of my Cassiopeia attempts at 105mm, as the W takes up most of the frame. Not much going on here though.

The rest of the astro snaps plain haven't been scanned (Only got a download of 26) which suggests they were blank and the guy didn't even bother scanning them.

Although it's a bit odd, as other shots that were scanned also appear blank, despite also being based on the camera's metering...

I plan on having another crack at this... But I definitely need to review my process!

Some snaps to judge the film on, or my photographic prowess haha.

Astro equipment is very sensitive to the quality of USB ports too. I always run my mount on a cable straight from the PC to the mount, never through a hub. The only hub I truly trust is my Pegasus Power Box Advance, which is the first one I've used that has supported even the fussiest pieces of kit.

I really like false-colour images made from mono Ha! Yours looks very clean and tidy as well!

I have only ever botched it without starless processing, but something potentially interesting that makes the nebula pop a bit is letting the Ha fade in saturation towards the highlights, if it's something you'd like the look of for your pics anyway.

I do like the moody red-only look