Filroden

Rotate it 45 degrees clockwise and I think I can see Iron Man's mask

1 hour ago, Gina said:

I now have Ha5, Ha3, OIII3, SII3

You're going to have some interesting choices to make about colour palettes with H, O, S and N to map!

Much cleaner!

And I blame you for my poor skies for the next few weeks. You've inspired me to invest in a Ha filter

My apologies for any forecast clear nights in the next few days/weeks that are now mysteriously cloudy. I just pressed buy on a Ha filter. Narrowband alt/az imaging here I come!

12 hours ago, Shaun_Astro said:

I only managed 60x30s subs and 10 darks before the lens froze over. Processing done in in light room and photoshop. The original had very bright streetlights in the bottom right which I managed to eradicate thanks to a tutorial vid by Doug German, a great channel!  I'm getting a 130pds tomorrow so hopefully should be able to produce better results in the future.

That's a very reasonable image with some nice star shapes (though they do start to elongate towards the top - maybe stop down the lens a little more?). You can just make out the Running Man and the Flame Nebula (it's clearer if you invert the image). I'm surprised you cannot see the Horsehead Nebula with 30 mins of total exposure, even with poorer Ha response. I don't think you've clipped the data (I couldn't find any 0/0/0 pixels, but there are some that are very close). Are you stretching the image in Photoshop and doing final processing in Lightroom? If so, do you stretch with levels or curves? I find curves harder but they preserve more detail if you do very small stretched many times. If the background brightens too much, you can always then do a final tweak with a small levels adjustment (or adjust the black/shadows sliders in Lightroom).

Good luck with the 130pds, I hope the skies are good to you!

38 minutes ago, Nigel G said:

Or it could be UFOs. 

Or UNOs (Unprocessed Nige Objects)

You can definitely see more definition in the modded version. But it's such a small target. It's almost worth cracking out the Barlow for it. 

2 hours ago, rotatux said:

What focus technique do you use ? I recall you are software-based, but do you also use a bahtinov ?

I have a mask for the SCT but now that I use SGPro I find it much more accurate to use the focusing tool within the software. I take continious 2s 2x2 binned exposures and SGPro analyses the star widths in the entire image (HFR). I adjust focusing until this number is minimised (always making my last adjustment in the direction that lifts the primary mirror). However, the focusing is very course. Even a slight turn can make a large difference. And even on a very heavy tripod, the whole system takes a long time to settle from any vibration. If I was serious about using the SCT I would add a new focuser to the visual back that had a finer control and could eventually be automated (which would reduce vibrations enormously).

3 hours ago, rotatux said:

Rather than boosting the green I would rather put in a bit less blue.

It's a tough decision to make on this target. I've seen RGB images that show quite a range of colours. My histogram in v1.2 has a balanced red/blue mix with the green slightly lower than both (it was much below in v1.1). The background in both v1.0 and v1.2 is more neutral than in v1.1 which had a red/purple cast (because I'd overdone the green reduction). So I think the stars and background are correct. However, I have so little data that even 15-30s extra in one channel is making a big difference.

I have more time later today so I may revisit the other subs I took (I took 60x1s of each channel as well as more 5s and 15s images) to see if I can align them and get a closer balance of total exposures in each channel. I may even have to dust off DSS. One of the problems I find with the SCT images is that there might only be 50-60 stars, so finding alignment is harder. With my refractor, I more often have 800+ stars so there is more to match.

3 hours ago, rotatux said:

And as time passes, my targets are getting out of my (limited) sight

I know that feeling. And the targets moving into my sight now are the galaxies in Leo and Virgo which either need the SCT to get real close and personal or a slightly longer focal length on the refractor (probably 800-1000mm).

17 hours ago, Filroden said:

 A puzzle for another day.

Whilst I still haven't solved the puzzle I was able to manually align 11 blue subs and redo my image. Not that 11x15s B subs adds much more data but I think the colour balance might be better (if not a little too red?). In theory, I could now go back through all my subs as some of the RG and L subs also didn't align. However, no matter what I do, this will never be a great image with such little exposure time and the problems I had getting focus and from the wind.

Version 1.1

Edit:

Version 1.2 with the green slightly boosted (to balance the red/purple hue). It probably needs more noise reduction, particularly the background.

It's a tough choice between going North to capture all the rich areas in Auriga or going South and getting the Seagull in Canis Major. I guess it will depend on how low your horizon is in that direction.

1 hour ago, Nigel G said:

Ken, amazing for such short time, good detail in there. I got a multi coloured blob from 60 minutes of 30s on M1.

Nige.

The individual subs were sometimes shocking. Blobby stars with slight bulges in which ever way the wind/passing cars would send the scope. I guess it shows the power of stacking. As each bad sub looked different to the next, they only really contributed where they were more consistent. I just wish I could figure out why my blue subs wouldn't align. The process could detect the stars but they could not be matched to the stars in any of the other subs (L, R or G) or even the combined images. They visibly look fainter in blue than the other filters but other than their actual size, about the same number of stars could be seen in R G and B so they should have matched. A puzzle for another day.

1 hour ago, Nigel G said:

The double cluster, 30 minutes of 30s and 20s. flats & bias. 150p, modified 1200d with CLS filter. DSS & ST.

I do love clusters. I've been so focused on nebula recently that I've not really looked at clusters but they do make nice images. 

I also managed a few minutes out last night (literally a few minutes). I got the SCT set up and focused to within a few miles of infinity (maybe a few thousand). So I had another pop at M1:

This is only:

B: 45 seconds (3x15s) (Although I had many more they just would not align with any other sub)

G: 105 seconds (7x15s + 1x5s)

R: 75 seconds (4x15s + 3x5s)

L: 415 seconds (26x15s + 5x5s)

So I'm pretty amazed there is even an image, let alone colour in the image  And please don't comment on the focus/vibration/tracking trails! If I'd discarded any more subs from the night I wouldn't have any.

Blimey, your 28mm lens can fit the entirety of Orion in it's field of view!

My SCT is outside cooling in the hope the wind stays away. I really want to see if I can capture anything useable in 5s exposures and M1 should be nicely placed.

1 hour ago, Nigel G said:

I'm quite amazed what colours have come out

Very ethereal! I wouldn't be surprised to see that win the Turner prize  I'd call it "Butterfly: are you pulling my wing?".

7 minutes ago, The Admiral said:

My tired old eyes aren't as all-seeing as Ken's, and I didn't spot any gradients

I'm not convinced there is a gradient but there seems to be a central brightness that seems unrelated to the reflection nebulosity, something that might be there if there were not flats applied and it was then stretched. But as you say, there is a lot of dust in the region and I've struggled to see what is dust and what is just gradient before (often incorrectly erring on the side of dust).

36 minutes ago, rotatux said:

Hi again, here's my progress on M45.

That's nice progress. Comparing the EQ with the latest AZ version it's interesting to see you have no star colour in the EQ image but the stars in the AZ image are very nice, showing a good range of white through to orange. I think the EQ image suffers most from limited total exposure time. Under 10 minutes of total time is not a lot, even for M45. You have twice as long on the AZ shot and I think the shorter exposures actually help retain the dynamic range.

I think there is still either a background gradient from light pollution or from vignetting. You don't say if you have used flats. I don't know processing software for Linux but I know both Photoshop (GradientXTerminator) and Pixinsight (DynamicBackgroundExrtactor) are both very good at removing background gradients.

Altitudes between about 30 and 60 are usually good - high enough to be above the worst of the light pollution but low enough not to suffer excessive field rotation. My concern with M45 at the moment is that it is also south. The combination of a southerly azimuth and high altitude means rotation is higher and you'll have to crop more. I think at my latitude (about 5 degrees north of you) I can still get 30s exposures in the area of sky.

I think to be fair to EQ mounts, a true side-by-side comparison between a good polar aligned, unguided EQ mount and a good aligned AZ mount would favour the EQ mount. Even unguided I would expect the EQ mount to be able to track for 60-120s without the issue of rotation and cropping. If you had 20x120s images from the EQ mount and compared them with 80x30s images from the AZ mount, you might notice less noise in the AZ image (from the extra stacked images) but you'd have better signal in the EQ image (from the longer exposures). It would be close though on a target like M45 with only 40 minutes of data. Now on a target like NGC1333 or M78, the EQ mount will be far better! The if you guided the EQ mount and were taking 2x1200s images...

I'd never claim we can beat EQ imaging, just that we don't have to be so far behind

6 minutes ago, The Admiral said:

and near to M1

I'd just noticed that. I'd probably still have given something a go but the wind will make it impossible. 

4 hours ago, SteveNickolls said:

Thanks Ken for showing what perseverance can bring, or is it a warning not to repeat as it is so difficult? I have an old 9.25" stored away and often wondered if it will ever see the light of day. Is your 'scope able to take a Hyperstar?

I think it was a little of both. To be fair, it was the clouds which caused the main imaging issue but it's certainly a much harder scope to work with than the refractor. 

I think it is compatible with Hyperstar but I think when I looked into it, it was not much more to buy the fast refractor. This gave me a 400mm scope compared to the 540mm that Hyperstar would give me. Given the difficulties I have focusing, I don't know how Hyperstar would work. I can at least add a new focused to the visual back that will be better than moving the primary mirror and could be automated. I do t know how Hyperstar could be focused other than moving the primary. 

Its supposed to be clear tonight but very windy. I'd still like to have ago at M1 just to see if it's worth doing other targets. I reckon I need at least 240x5s subs for each of LRGB to even start getting something reasonable. Ideally I would test 10s and 15s subs but if their fail rate is too high I'm safer staying with short subs and increasing the camera gain.

One step forward, seventeen steps back...

I now remember why I never liked trying to image with the 9.25" SCT. I bought myself a new finder base for the SCT so I could easily swap the finder scope and StarSense between my two scopes. Tonight was supposed to be cloudy but it had been crystal clear all day and as the sun set it was still clear. I thought I'd give the SCT a whirl as I'd not used it since buying the refractor.

I got set up and did my first StarSense alignment. There was already a few clouds starting to form. After aligning I did a goto to Capella to focus and see how good the uncalibrated alignment was (it was currently calibrated for the refractor). No bright star in the field of view but I could at least see three or four nice big doughnuts of out of focus stars. Previously I think I would be lucky to see even that it was often so far from focus so it was pretty easy to a. figure which direction to focus and b. bring it to a close focus. Then the fun began and I had my first reminder of why a 2350mm focal length scope is a beast. Any slight movement of the focuser and the whole image would wobble, taking a good few seconds to settle. By which time a small gust of wind would have set it moving again and another wait, by which time a kid playing in the street would have made the ground tremor enough to set it wobbling again.

I thought I'd try the Bahtinov mask. Not a chance. So went back to minimising HFR and patiently got it to a score I was somewhat happy with. Now to find Capella. I noted the position of a star in the centre of the field of view then manually slewed it to each corner in the hope Capella would appear. Not a chance. So I did a plate solve and finally found I was about three fields of view away. It didn't take me long to find it. And boy was it huge. I thought I'd hit the moon or something. So I calibrated on Capella and did a fresh alignment.

A quick goto to M1 later and I found the stars I was looking for to know I had M1 close to the frame. I was running continuous 1s exposures at this point so no sign of M1 even with a light stretch. Checked outside. That nice grey even background I was seeing between the stars...more clouds...but some gaps, some of them big.

So I upped the exposure to 5s and just watched each image. Slowly, as a cloud moved, I'd see a cloud in the centre of the field. Could it be? Yep, it looked the right shape to be M1. So I thought this was a goer. I tried to improve focus a little more. Think I'm going to need a new focuser if I am going to persevere with the SCT!!

I also tested a 10s exposure which seemed to work but not as well as 5s in terms of good frames, so I decided on 5s.

I set up a sequence of 12x5s each for LRGB in the hope of doing short runs I could get something between the clouds. I ran it twice by which time the clouds were totally obscuring the target and they were so dense on the horizon I packed up.

Of the 96 images most were affected by clouds. I decided not to even care and ran a star alignment on them using a good L frame as reference. Only 2 of the 24 B frames had enough stars to match. More of the G, L and R frames gave star matches and in total I had 42 images that could be aligned.

Now normally I'd really check each frame and ditch any that had clouds. But with only 42 frames I just didn't care! I threw the lot (LRB and G) into a single integration in the hope enough signal would climb above the clouds. There was no chance of integrating them separately though I did test with just the L frames and it was similar in result but just a little noisier. So all I had was the certainty that I could align my SCT still, I could just about focus it, and it would just about take 5-10s images.

Here's a very poor mono M1 with just over 3 minutes of LRGB data all combined. Oh, and did I mention the Moon was just out of frame?

Hi and welcome to the thread. I hope you'll post your results here once you're into imaging

In reply to your question (and the question you've posted elsewhere as they are all related): what do you need to get into imaging?

Mount

You have a good altaz mount. Mine will keep my target centred for many hours once aligned. This is great for visual use but not actually all that important for imaging (even though it's helpful) because of other limitations linked to the altaz nature of the mount which mean you will be restricted to individual exposures of under a minute or two. Altaz mounts track differently to EQ mounts and suffer an effect called field rotation. The mounts hold the camera in the same absolute orientation related to ground, so as the stars move across the sky, they will rotate within the image. The easiest way to understand this is to look at Orion when it rises in the early evening and check it again a few hours later - he starts leaning to the left in the evening, he is upright when he passes south and he leans to the right when he sets. The same thing happens in your images. This can be worked around by taking shorter images so there is not enough time for the rotation to be seen. However, you still see rotation between each image and when you integrate the images you will see this. We have to crop our images to remove these stacking artifacts around the borders. I can lose up to 30% of the image if I have been taking images over a very extended period.

The goto accuracy of your mount is also very good and it's very easy to align (even easier with the StarSense accessary but that's just a time saver - you can get as accurate an alignment using the two or three star methods). I found the wifi useful and used to control the mount from my iPad but it can be temperamental. I think my issues with wifi were that my iPad would try reconnecting to my stronger home wifi over the scope's weaker wifi signal. Once it drops like this, I found it impossible to reconnect and had to get the handontroller out and do a new alignment (you cannot align with one and use the other - which even method you use for alignment needs to be the method you use to send goto commands).

Scope

Again, a great scope and ideal for visual. It's also very good for imaging lunar and planetary targets, especially when combined with a barlow, because they are so bright and you only need exposures of a second or less. It has a very long focal length at just over 2 metres. As a reflector, it doesn't suffer chromatic aberation (where light of different colour is focused at slightly different points) so you will get good colour once you reach sharp focus. You'll probably need a dew shield as a minimum. The corrector plate will mist up quite quickly without one. I use a shield but no heater.

Now about that focal length...this is where you'll run into problems with imaging. The first is the field of view (which will depend on your choice of camera). With a standard DSLR you won't be able to fit much of the biggest DSO's into the field of view, e.g. M31, M42 or M45. You could just about fit M33 into the field but with field rotation you would lose much of its arms when you had to crop. Realistically, at 2m focal length, you'll be targetting DSOs like M1 or M51. You could add a focal reducer. The most common would reduce the focal length by 1/3rd but I don't think that would bring any of the big DSOs within range.

So you will need to decide what type of targets you want to image. The big (and bright) targets would probably be better suited to scopes with focal lengths of 800mm or less. My refractor has a 400mm focal length and gives me nice wide fields with both my cameras. My 9.25" evolution is reserved for planetary targets and small galaxies.

The second is that longer focal lengths need very accurate tracking. If not, you are limited to shorter and shorter exposures to avoid star trails. I found I could only get a maximum of 15s exposures with the SCT (2350mm focal length) and more often would actually only get 5-10s. My refractor, on the same mount, lets me take exposures of 30-120s.

So with your scope, you'll be probably hunting fainter targets which would prefer longer exposures but you'll actually have to take shorter exposures. Even this can be worked around with the right camera or filters or a good, dark location.

Work arounds

You'll here this a lot on this thread. We know we're not imaging the best possible way. But we're imaging with the tools we already have, can afford or choose for other reasons. We don't expect the same results but we like to get the best results we can with what we have.

If you were just starting out with no equipment, you will get different recommendations that if you are trying to use equipment you already have. Never forget the advice here is always a compromise between what would be better/best and what you could more easily achieve so long as you accept the limitations.

Camera

This is the other half of the equation for imaging and it's chip size also defines the field of view when combined with the scope's focal length. There is a really useful tool on the First Light Optics website for showing field of view with different DSO targets and combinations of scope/camera at http://astronomy.tools/calculators/field_of_view/

If you already own a DSLR I would recommend trying with this first. All you need is an adaptor that fits directly onto the DSLR body and ends with a nose that fits into the scope in exactly the same way as an eyepiece. The better way of attaching the camera is a fully threaded method but this requires a few extra adaptors (though the cost difference isn't that large). Using an existing camera will give you the chance to see if you're happy with the images you can get from the mount/scope. DSLR's have some of the widest fields of view so any camera upgrade is likely to be similar or have a smaller field of view.

I started with a Canon EOS60d. I had one for daytime photography so I wanted to use it. Eventually its downsides put me off enough to upgrade. My camera had a lot of noise. You cannot cool them without a lot of modification so the chip ran at over 20C which causes a lot of noise. You cannot easily use darks to calibrate because you cannot match temperature. I also didn't like the sensitivity of the camera. one-shot colour cameras have to divide the chip up to particular colours so you're not using the full power of the camera. Half of the chip detects green light (great in the daytime, not so great for us) and only a quarter is dedicated to reds and to blues (much more interesting for us). Also, one of the main sources of red, Hydrogen Alpha, falls in one of the least sensitive parts of the chip. I think my camera could only capture about a quarter of the actual Ha data because of its efficiency - so I was only getting a quarter of the data on a quarter of the chip! Again, you can modify the camera to improve its red sensitivity.

I went for an upgrade. I went to the ZWO ASI1600MM-C. It uses the same chip technology as a DSLR (CMOS) but in a astro-dedicated package. It's a mono camera so I use it's full capacity. It's more sensitive to reds. It's cooled so much less noisy. And it has a very low read noise. So shorter exposures work well with it. It does however only have a bit depth of 12 (so it can only measure light strength on a scale up to 4k). My DSLR had a 14bit depth (so four times bigger) and most CCDs have 16bits (so measure light on a scale up to 64k). Bit depth is important as it limits the amount of contrast you can achieve. You can overcome this by taking lots and lots of exposures. If I take 4 exposures, I can get back to the bit depth of a single exposure from my DSLR. If I take 16 exposures, I can get back to the bit depth of a single exposure from a CCD.

The ZWO camera came with everything I needed to attach it to my scope other than spacers to get the back focus spot on (something I still haven't fixed yet).

Filters

Light pollution: if you live in an area with lots of light pollution from sodium and mercury lights (bright orange glow) then light pollution filters will help you take longer exposures without overexposing because of the background light. However, these don't work for LEDs because they shine with broad spectrum white light (boo).

Broadband colour filters: if you go the mono route, you need RGB (and probably L) filters so you can combine them to get colour images. I use LRGB filters in an electronic filter wheel so that I can automatically swap filters during imaging. My L filter is just an IR/UV filter to cut off non-visible light (which stops star bloat). You can use a light pollution filter as an L filter too.

Narrowband filters: you can get filters which are limited to very small ranges of light that match up with the main sources of light in emission nebula such as H alpha, SII and OIII. You can also get them for N, H beta, but these are less common. They come in various "widths" which shows how tight they are. The narrower the filter the more expensive it will be. Because they only pass through a limited range of light they usually need longer exposures (or very bright targets). Again, my camera has some nice capabilities that mean you can still get reasonable results with exposures in the 30-120s region - in range for my refractor but no good for my SCT.

Capture method

With a DSLR you can just attach it and click away (remembering to allow pause time for the vibrations to settle). No other equipment required. Or you could hook you kit up to a laptop and control it from there. You'll also want to consider processing software both for integrating the images and then developing them.

Second health warning

Your mileage might differ to mine  I've found solutions that I like working with and give me results I'm happy with. I've thrown a lot of money at making it easy rather than making it good (though it has made it much much better). With the same budget I could have got an EQ mount and got better results but at the cost of ease.

As I said before, give it a try first before investing a lot. Use (or borrow) and existing DSLR and give it a test. See if you like/enjoy the results and then see what you want to achieve. The more you know what you want to acheive (choice of targets, field of view, etc) the easier it is to give more specific advice.

54 minutes ago, The Admiral said:

I cannot fathom what deconvolution is doing in ST. ST seems to mask stars with a rounded square

In Pixinsight, I create a star mask to protect the stars from getting rings and I also mask the background to prevent it being sharpened. The mask is usually always a little bigger than the star. I also have the option of calculating the point spread of stars by selecting them (it was recommended to select about 50-60 stars to get a good average). Alternatively you can just use a default star shape. As I got similar results from both, I chose the easier option! I guess the star masks/deconcolution in ST are doing the same thing. It does sharpen and reduce the stars, making them much nicer shapes. I haven't noticed much improvement in other areas and I sometimes skip deconvolution entirely if I'm already happy with star shape.

14 minutes ago, rotatux said:

Err, for now my mount is quite reluctant to this :-/ : trying 30s gave a reject rate of about 85%, so I must be careful. I am working on M45 image where I pushed to 20s with only 26% rejects, so I try improving until I can find the root cause for this mis-behaviour.

M45 is almost due south in the early evening so has the worst rotation. I normally avoid targets close to the meridian or reduce my exposures to 15-30s depending on altitude.

1 minute ago, The Admiral said:

Ha ha, I think I actually pushed the magentas more towards the red in Lightroom!

I think that's the right call, but hue adjustment in Lightroom is in quite narrow ranges so you've got a good balance of the red shades within themselves but probably a little out of balance overall (if that makes sense). So I would keep your reddened magentas (and possible bluen your purples) but change the overall tone with the temperature slider towards the blue (maybe only by a couple of points). I'd usually do this in Photoshop as I would just slide the R levels back a little. I think if you checked the RGB histogram your red channel will be far ahead of the blue (which is right, it is a red dominated image, but probably just a little too far ahead).