SteveNickolls

Well the 'No EQ Challenge' thread is the second most viewed thread in the Getting Started With Imaging section with 36,491 current views and as Ian points out is the thread with the most replies so is a very active one especially for the number of people involved. Who could have imagined that what John (JHG1971) started back in October 2014 would continue to grow, and at pace to the present day?

As regards to having a separate section for our interests I was in the past unsure if it would pigeonhole Alt-Az imaging but I have now embraced the view that by setting up a dedicated area it allows the various components such as our images, equipment, techniques and guides to 'how to' or 'where to go' to be made more accessible to everyone and we can begin to lay down a store of knowledge that simply either didn't exist before or were certainly buried and often when uncovered were not linked as a whole.

The same factors that influence us imaging tonight and which brought Joseph Ashley to the point to write his book, 'Astro-photography on the Go Using Short Exposures with Light Mounts' remains a constant to every new, potential imager. Part of the answer comes down to daring to enschew the orthodoxy requiring the buying of very expensive equipment in order to try out imaging and instead to first 'dip their toes' using a low cost, portable, lightweight Alt-Az or EQ mount and telescope plus the family camera. For many people the choice boils down to either trying low cost imaging solution or not imaging at all. Developments in technology have helped permit low cost imaging and I see the future of highly sensitive CMOS cameras needing much shorter imaging times as further opening up imaging on lightweight mounts to more and more people.

Cheers,
Steve

1 hour ago, Nigel G said:

Its the Astronomik CLS CCD deep sky & Light pollution filter Canon clip fit.

It will work better with the modded camera.

I need to get a set of subs to see how it performs.

The write up says, Good with un modded , very good with modded cameras which is the reason I chose this one. With un modded camera there will be added contrast,

 

There is a loss of detail in the same exp time for sure. Hopefully not a waist of money!

Nige.

It will be very interesting to see how your filter performs with a target object Nige :-) Will you be doing a 'with' and 'without' filter for comparison?

I took delivery of a Baader Semi-Apo filter and 2" adapter for my refractor earlier this week which has some light pollution reduction value along with the at source fringe killing ability. Just need the clear night to use it now.

Regards,
Steve

5 hours ago, Filroden said:

So, here's my first attempt at NGC1333:

You can already see some of the dark area surrounding the object. Hardest thing imaging dark on black but perseverance will pay off.

Cheers,
Steve

5 hours ago, Nigel G said:

Any thoughts ?

Hi,

I would always try to image individual frames as long as you can to improve the S:N ratio for the fainter parts of your image. I would add the caveat that there's a personal decision to be made on what is bearable in terms of successful images which DSS will accept. If practice shows that a very few much longer exposures in a stack greatly improves the overall image then I'm in favour of it despite the big hit in wasted time. I have never tried imaging longer than 70 seconds thinking the time loss was more important but it would be worthwhile to now try. More importantly I've never stacked exposures of different times to see the benefit. Thanks Nige.

Since last December I've kept a record of the percentage success rate of images in DSS from different exposure lengths, really carrying on the technique suggested by Joseph Ashley in his book, but in this instance covering thousands of light frames not a small number. The results show the mount and imaging equipment do quite well over a wide range of exposure times but start to show a significant fall off at 50 seconds and an inconsistency in performance up to 70 seconds. I'm believe wind has some effect on the success of frames but mostly any reduction in acceptable frame numbers is down to the mount design and it's (in)capacity to perform long tracking. The average percentage of frames for exposure duration are listed below.

10 seconds 79%     Mostly taken early on in my imaging of DSO's

25 seconds 94%

30 seconds 90%

40 seconds 90%

50 seconds 68%

60 seconds 76%

70 seconds 43%

I'd expect the percentage rate of acceptable frames would continue to drop beyond 70 seconds but if the few successful ones provide a significant improvement in the final image then they are worth taking and adding to the stack.

Interestingly I have done a number of wide field imaging sessions taking images with my camera piggybacking on the mount and telescope and never had less than 100% frames acceptable to DSS (these are exposures between 40 and 60 seconds). Any trailing is probably better hidden by the wide field image. I believe wide field images could be taken well over the exposure limit of images using longer FL's provided the limits of field rotation are not grossly exceeded. Worth an experiment.

So thanks for this moment of thought provoking Nige.

General plea-can we now have a clear night please to practice?

Cheers,
Steve

1 hour ago, The Admiral said:

An alternative may be something like this : https://www.firstlightoptics.com/alt-azimuth/skywatcher-l-bracket-dovetail.html

The only issue might be aligning on a star without a finder if the camera lens doesn't offer a very wide view. I guess if you are using a zoom, then finding your way around might be eased. I've not personally tried this though, so others may correct me.

Ian

Ian hits the nail right on the head regarding alignment. For very wide shots accurate direction is not so critical but as you increase the FL of your lens it becomes important to be pointing right. Even more so if you need to slightly adjust the framing. You will also find that even very bright stars only come into view (if you use Live view or similar) when very close to focus and it's easy to get frustrated. That's why I have gone to the lengths I have to ensure camera/eyepiece and finder point exactly together as it saves time and bother later. It's also important to take your time getting the best focus and I've found moving the focus in and out a few times helps you best judge things. Some cameras have a magnification capability in Live View to help with focusing. There are pieces of software (APT and BYEOS/BYNikon) that can help for some makes of camera but TBH you're far better left doing things manually for now. I usually take some trial shots to check framing of the object and adjust as required. For very wide view shots again it's not an issue. Some camera lenses creep in use and move out of focus due to gravity. Not had that problem on my Canon 75-300mm lens but worth keeping an eye out when you first use your lenses.

Cheers,
Steve

9 hours ago, Yamez said:

I shall try putting a brick on the tray, how would i piggy back the camera on the telescope? Will i need special equipment?

Hi,

+1 to what Nigel G has said. My own approach was this but for a refractor-

I bought an extra tube ring so I can mount the camera on the side or top of the telescope and a ball head to allow for collimation of the camera with the eyepiece/finder. The arrangement has performed fine with no unexpected movement of the ball head or camera. The Synscan mount has proven a good workhorse even with all the extra parts that must affect balance. 

Good luck.

Steve

Hi Yamez,

One 'technique' I use with my Synscan Alt-Az mount is to place a house brick in the eyepiece tray, it's 3kg mass helps to steady the mount, it might work for you. Another is to centre the alignment stars with an eyepiece with a cross hair. As others have said I think your limitation is having to use the barlow lens. You could try some wide view shots having your camera piggyback on the telescope as the mount tracks. You will need to align your finder/eyepiece/camera. I bet you will get longer and accurate tracking that way and some targets are better framed in wider fields.

Cheers,
Steve

7 minutes ago, parallaxerr said:

Yep, exactly that Steve. At about 62°, the camera contacts the base of the mount. I may be able to address this by fitting a long dovetail bar and sliding the whole lot forward as it's quite tail heavy at the moment anyway.

 

Ahh, thanks for the clarification. Yes a longer dovetail bar way well solve your problem-good look experimenting. 

Cheers,
Steve

8 hours ago, parallaxerr said:

"... The only problem I have now is the Alt limitation of the mount which puts a stop to M31 imaging at around 10pm."

Hi,

I'm curious to know what restriction your mount is causing you, is it because of potential collisions of the telescope and mount? Anyway good luck amassing frames of M31.

Cheers,
Steve

2 hours ago, Nigel G said:

20 minutes ago I set up my mount ready for the scope,  the sky's were gin clear all round,  I just made my dinner and could hear a sound coming from the conservatory observatory.  Popped out and it's bucketing it down with rain. Mr weather man said clear sky's all night.  

Hopefully just a passing shower, anyway mount indoors and dry now. 

I need a new weather man 

Nige.

I do hope you had the mount covered to stop the wet getting in Nige. Ian is right about the poor weather forecasts of late, and it doesn't help that the weather too is plain poor. This October so far has been the worst for observing since I started keeping records in 2012-13 and September was joint worst with 2012-13, I hope it improves before long. 

Cheers,
Steve

Hi,

I'm steadily working my way through my back catalogue of images and reworking in DSS and StarTools. Here is an image of the Flame Nebula and The Horsehead Nebula (Barnard 33) first imaged in February this year when the objects were 'best' placed for me to image in the South, but over the light pollution of the Nottingham conurbation. The image is much improved on my first processing attempt but there is still evidence of light pollution in the final image. It was made from x182 thirty second light frames at ISO 1600 plus x50 dark and x50 bias frames. At the time I wasn't taking flat frames. The equipment used - my SkyWatcher Startravel 102mm refractor (f/5), Synscan Alt-Az mount and Canon 600D DSLR.

Cheers,
Steve

26 minutes ago, Nigel G said:

The weatherman was wrong, I had intermittent clear sky's this morning between 2.30 and 4.30 . I managed to get 30 mins on M42 despite the full moon.

10 minutes of 10 seconds and 20 minutes of 20 second exp. plus 70 dark and 45 flat @ 1600 iso, The core is over exposed so I'm trying stacking the 10s subs alone.

Its a nice neb to image as there's plenty to look at on screen, it's my first attempt at stacking M42 and I'm pleased apart from the messy core.

I tried short subs to get a sharper image, I think its worked, the 10s stack should tell.

150P Canon 1300D DSS & ST, touch up in PS express, Alt-Az goto.

Any ideas on core exposure welcome  

Cheers

Nige.

Well done with M42 Nige, both capturing a nice image and being able to get up at 'too early in the morning' to image at all :-) I can't help about combining different exposures but I bet it's in the StarTools guide.

Cheers,
Steve

24 minutes ago, Stub Mandrel said:

You might find the graph in this thread interesting, made by looking at dozens of Exifs...

A very interesting read indeed Neil. I guess each equipment set up will slightly affect the temperature variation experienced (e.g. if the camera sensor is behind a filter etc) so there's value in checking your own situation and seeing how temperatures vary over a session. I will be recording external temperature over my sessions from now on and even if it is not 'scientific' using calibrated thermometers it is still an insight into how temperature varies over a period and maybe I can make a better informed decision over whether to use dark frames in the future or not. I will also look at the software EXIFLOG. Thanks once again.

Best Regards,
Steve
 

10 minutes ago, Stub Mandrel said:

You might find the graph in this thread interesting, made by looking at dozens of Exifs...

Thanks Neil for this, will take a good look at the thread, it's a most interesting subject.

Cheers,
Steve

With the current poor weather affecting Alt-Az imaging sessions I recently decided to take out a trial of BYEOS. I was interested to find that BYEOS actually obtains details of the temperature of the camera (no one knows where the sensor is located so it may not be on the chip of course but a guide to the internal temperature of the camera nonetheless). For a short while now I've not been using dark frames with my images and this ability to record internal camera temperatures will be useful to see how temperature varies over an imaging session. It has implications of course for imaging in Alt-Az with our extensive numbers of light frames. I've checked the exif temperature data for two imaging sessions, the first on the 17th March this year. The session was split into two main sessions allowing me to adjust the position of the object in the finder scope as it was a long session. There was a second interval between images and the big division to recenter M51 lasted 1 min 37 seconds.

M51-

Frame number   Sensor Temperature (degrees C)

1382                                23

1391                                20

1400                                18

1409                                17

1418                                17

1427                                16

1436                                16

1445                                16

1454                                16

1461                                15

Break of 97 seconds

1462                                13

1471                                15

1480                                15

1489                                15

1501                                15

The results are very interesting. I'd guess the camera was cooling down and slowly reached 15 degrees. An interpretation could be-the outside temperature may have been lower that 15 degrees and the camera cooled more while it was not in use then tried to rebalance itself at 15 degrees when images were once again taken. I'm going to check other image sessions where there were different imaging lengths and intervals between images. Pity I didn't take the ambient temperatures at the time, never mind that. What purpose are temperature dependent dark frames? :-)

NGC 1499-

A more recent imaging session on 2.10.2016 involved taking x91 sixty second images of NGC 1499 at ISO 800. The camera had been placed outside in the afternoon so had time to cool down before use in the evening. The were three divisions of images taken as I was using my intervalometer to take x30 frames in a session-

Frame number   Sensor Temperature (degrees C)

4878                                  16

4887                                  18

4896                                  18

4905                                  18

4907                                  18 

Break of 2 minutes

4908                                  17

4917                                  19

4926                                  19

4935                                  19

4937                                  19

Break of 5 minutes

4938                                  20

4947                                  21

4956                                  21

4965                                  21

4967                                  21

Interesting goings on there.

The next time I run an imaging session I will record the external temperature to compare the camera sensor value with posthumously.

Hope this proves interesting to others :-)

Cheers,
Steve

I'm well pleased you enjoyed that bottle ;-) Either a good accompaniment to an imaging session or as an alternative. We did a tour of some of the Western Isles and Oban earlier this year but didn't quite get as far south as Jura unfortunately. 

Cheers,
Steve

13 hours ago, Nigel G said:

Oh for a clear night sky, I sit here swirling and sipping a single malt thinking what I'd do for a whole night of clear sky's, the weather man says no clear sky's for the next 5 nights. I really hope he's wrong.

Doesn't he know we have lots of things to try....... I'm going to re process an image or 2 with the recent findings.

This will be my 3rd reprocessing, it is great to be able to go back and start again with anything from re stacking to final tweaking ( depending on weather you kept your sub's )

I hope your weather man is telling you better things.

Cheer's

Nige.

 

Hmm, the weather forecast here is pretty poor too, can only be consoled that it's a bright, full Moon. Plenty of old images to reprocess though. Can I ask which whisky you are sipping?

Cheers,

Steve

1 hour ago, alacant said:

Hi. No, not piggyback; in the telescope as you're imaging. It's a 2" filter you screw onto the nosepiece to which the camera is attached. I think uv is part of it but you also need to cut the ir, one stops the core of the star expanding, the other the blue halos. There's one filter which does both and controls the way the sensor sees the blue or uv or ir or some combination of them. I'm no expert so sorry can't be more specific, I'm away at the moment but there's a photo of it in the link I sent. HTH

Thanks, I'll take a look at the filter. :-)

Cheers,
Steve

24 minutes ago, alacant said:

We've a thread on the st forum about reducing the halos, not just in software. I found by accident that there are methods at the image acquisition stage too. On my modified canon the remaining filter is not enough to avoid the stars enlarging. The uv (or maybe it was the ir -tech stuff I don't understand) records as blue by the sensor. A filter will remove all the invisible radiation and in so doing all but remove the blue star halo. HTH.

Thanks for this alacant my camera has  standard uv filter on it when used for piggyback imaging is that what you mean? I'll take a look on the StarTools Forum too. I have tried removing the blue channel in the past and that can help.

Cheers,

Steve

1 hour ago, happy-kat said:

Really interesting comparing those. There is a much smoother background with the second image it's lost the mottling noise. Be really interesting to see if you can do this but say on m31 as that might be tricky with how m31 is.

Thank you for sharing.

Hi, I'm unsure how a galaxy also being in the image would respond but there's really only one way to see :-) I've just re-stacked the origianl frames and processed an image of M35 from the 16th January 2016 using the same method, again just a shot with stars and clusters.

Here's the original image (from x30 ten second light frames at ISO 1600 plus x40 dark frames) at the time I hadn't got to he point of taking flat frames or bias frames. All exposures using the SkyWatcher Startravel 102mm refractor and Canon 600D DSLR on the Synscan Alt-Az mount-

At the time I hadn't known how to remove the purple halos around the brighter stars.

And after the new procedure, the image has been cropped more in the latest attempt this afternoon-

The smaller cluster at the four o'clock position  is NGC 2158.

Cheers,
Steve

48 minutes ago, alacant said:

Great shot. Nice technique. Even better colour. Who needs an apo?!

He,he thanks, I was wondering that myself.  Might see more in the classifieds.

Cheers,
Steve

I've been playing on StarTools again and come up with a potential way of getting an image with a background clear of light pollution. It will work in images where there are just stars. I follow the process in the HEAL section of the StarTools 1.3.5 Unofficial User Manual (p 83 onwards) but use the extracted stars as the final image. What do folks think?

Here's an image of NGC 1502 taken on 15th August earlier this year (x20 forty five second light frames at ISO 800 plus x50 dark, flat and bias frames stacked in DSS and processed in StarTools). I used the SkyWatcher Startravel 102mm refractor on a Synscan Alt-Az mount and Canon 600D DSLR.

Image processed without the new process showing remaining evidence of light pollution-

And using the new procedure for comparison-

Regards,
Steve

On 10/13/2016 at 12:07, Nigel G said:

"...It looks good but I think we with alt-az mounts might struggle a bit with having to crop and the field rotation thing. I think it will be a lot of work trying to line up the images."

Nige. 

I've downloaded a trial version of BYEOS Nige and one of the things you can do (p30-31 of the BYEOS manual) is overlay the current imaging session with an image from a previous session to align everything up (called 'Mask Framing in BYEOS'). I haven't tried this yet but it might be worth investigating? As an alternative I have used DSS to combine the images from two sessions and it is very forgiving.

Cheers,
Steve

2 hours ago, alacant said:

**Î've a feeling we're gonna get thrown off this thread soon as I think we may have gone off topic. Me certainly.

I would hope not-no one has said anything up front about matters as far as I know. It has become a very popular thread though hasn't it?

If it wasn't to pigeon hole us Alt-Az'ers more I'd ask for a separate Alt-Az Imaging section in SGL to keep the particular issues together and available for others to find and participate in. What this thread has done is to act as a focal point for a growing a body of like minded individuals who are up for experimenting with equipment and software and having a place to post their successes and issues, and importantly, discuss. If the posts were split up across SGL then I'd be asking for a place of our own. We are posting images and most importantly detailing our settings etc. so others can learn from them. Using StarTools for Alt-Az work is different from using EQ gear as we are touching on important issues around light pollution, the length and number of light frames, the point of using dark frames and the issues surrounding using and applying software to Alt-Az data. If it wasn't for Alt-Az imaging a number of people would never have taken the practical steps to get into astro-photography and be put off by the common but misconceived  view that you can't image with Alt-Az gear and so...

As a way of demonstrating the interlinked nature of Alt-Az working I'm posting an image of M51 that I have been able with the help of this thread to better utilise software (DSS and StarTools) over seven months to improve the final image-

First my earlier attempt-

And the same data after tweaks to DSS started and discussed on the thread (and also for StarTools)-

The data used 115 forty second light exposures at ISO 1600 plus x50 dark and x50 bias frames. At that point I had not been using flat frames as part of my learning curve. I used my SkyWatcher Startravel 102mm refractor on the Synscan alt-Az mount and Canon 600D DSLR.

You can still see the effects of local light pollution in the more recent image.

Ad Astra Guys,

Steve

And as alacant says do BIN as the first process in StarTools to reduce the working file size down and quicken up the subsequent steps, then CROP :-) 

Cheers,
Steve