Second telescope image M64

[Nigella Bryant]

Hi all, my second image taken with my 12inch f4 Newtonian of M64

[alan potts]

Nigella, If you include details of what you did some members with more knowledge than me may well tell you how you can improve your images and capture technique. They have helped me no end the last few weeks. This is clearly a good start and I am sure you are pleased, I know I was when I started but then hit a brick wall with all sorts of issues, many not my fault.

[Demonperformer]

Agreed. Very good start, but it is difficult to know how to advise on improvements without a few more details; camera, number of subs and their duration, what calibration frames you did - that sort of thing.

[Nigella Bryant]

Hi, thanks for replies.  The image was taken at prime focus using a Canon 1000dm for lights and 10x45second exposure at iso800 staked in DSS and photo shop CS2. 4x45secs dark frame's were used as calibration frames in DSS but I know I need to add more data and take some flat frames too. It was unguided on a Neq6 mount so need to guide at some point and also get a light pollution filter as I live in a bortle 6 sky area on the outskirts of a small city.

[tooth_dr]

1 hour ago, Nigella Bryant said:

Hi, thanks for replies.  The image was taken at prime focus using a Canon 1000dm for lights and 10x45second exposure at iso800 staked in DSS and photo shop CS2. 4x45secs dark frame's were used as calibration frames in DSS but I know I need to add more data and take some flat frames too. It was unguided on a Neq6 mount so need to guide at some point and also get a light pollution filter as I live in a bortle 6 sky area on the outskirts of a small city.

That’s a nice image Nigella. If I may make an observation - 4 dark frames is not enough. Maybe 50-100 would be more like it.  But then again darks aren’t even really used by a portion of DSLR images  

 If you start guiding you can make use of a process called dithering.  That way you can stop using darks altogether.  I didn’t use darks with my modded 1000d.

For flats - stretch a white t shirt over the end smoothly, held on with an elastic band, set camera to AV and again take 50-100 flats.

 

Good luck!

Adam

 

[Nigella Bryant]

14 hours ago, tooth_dr said:

That’s a nice image Nigella. If I may make an observation - 4 dark frames is not enough. Maybe 50-100 would be more like it.  But then again darks aren’t even really used by a portion of DSLR images  

 If you start guiding you can make use of a process called dithering.  That way you can stop using darks altogether.  I didn’t use darks with my modded 1000d.

For flats - stretch a white t shirt over the end smoothly, held on with an elastic band, set camera to AV and again take 50-100 flats.

 

Good luck!

Adam

 

Hi, what is dithering,  I thought it was at the supermarket not knowing what to buy, lol. Seriously how does one go about this technique? 

[Demonperformer]

It is a process that causes the scope to move a few random pixels between each sub. This moves any constant noise to a different bit of the final picture and so it is cancelled out when the subs are stacked. There is a setting in PHD2 (and presumably other guiding progs) to set it up.

[Datalord]

If I may suggest something, wait with the whole guiding thing until later. It introduces a vast amount of complexity to your imaging runs you just don't need as a beginner. Darks can be taken once during daytime and then you have them for a long, long time.

Instead, focus on taking many more images of a single target with shorter intervals, say 15 sec. Capture at least 4 hours of data on one target and hone your processing skills, they will get you very far regardless of equipment.

Good beginning, welcome to the time and money sink.

[tooth_dr]

23 minutes ago, Datalord said:

If I may suggest something, wait with the whole guiding thing until later. It introduces a vast amount of complexity to your imaging runs you just don't need as a beginner. Darks can be taken once during daytime and then you have them for a long, long time.

I definitely wouldn’t recommend using darks, and especially those taken during the day. For the OP 1000d DSLR this isn’t correct.

[Datalord]

32 minutes ago, tooth_dr said:

I definitely wouldn’t recommend using darks, and especially those taken during the day. For the OP 1000d DSLR this isn’t correct.

Why?

[Nigella Bryant]

Now I'm confused, to dark or not to dark, that is the question.?

[JamesF]

30 minutes ago, Nigella Bryant said:

Now I'm confused, to dark or not to dark, that is the question.?

Whether 'tis nobler in the mind to suffer the amp glow and background noise of outrageous exposure times, or to take arms against a sea of artefacts and by stacking, end them: to image, to sleep no more; and by a sleep, to say we end all chance of capturing that faint nebulosity.

James

[Demonperformer]

The thing about darks is, to be effective, they need to be taken with the chip at the same temperature as the lights. This is a combination of ambient (air) temperature and the energy being released as heat during the imaging process.

With a cooled camera, you can determine the temperature of the chip precisely, whenever you take the darks, and so they can be done anytime. With a DSLR you do not have that option (normally) and so they need to be taken at the same time as the lights to get them as closely matching as possible.

Badly matching darks are worse than no darks at all.

For short exposures, it is easy enough to cover the scope and run off a set of 10-20 darks at the time. For longer exposures (>60s) it can start to eat into prime imaging time!

[Nigella Bryant]

4 hours ago, Demonperformer said:

The thing about darks is, to be effective, they need to be taken with the chip at the same temperature as the lights. This is a combination of ambient (air) temperature and the energy being released as heat during the imaging process.

With a cooled camera, you can determine the temperature of the chip precisely, whenever you take the darks, and so they can be done anytime. With a DSLR you do not have that option (normally) and so they need to be taken at the same time as the lights to get them as closely matching as possible.

Badly matching darks are worse than no darks at all.

For short exposures, it is easy enough to cover the scope and run off a set of 10-20 darks at the time. For longer exposures (>60s) it can start to eat into prime imaging time!

To dark then, is the best, in my mind during those sleepless night's whilst my beating heart shivers. I will endeavour in a session of next night of clear cloud's to engage in the sphere of the heaven's as my scope penetrates the darkness. 

[Datalord]

6 hours ago, Nigella Bryant said:

To dark then, is the best, in my mind during those sleepless night's whilst my beating heart shivers. I will endeavour in a session of next night of clear cloud's to engage in the sphere of the heaven's as my scope penetrates the darkness. 

No, do it on a cloudy night so you don't eat imaging time. It's more important to get proper data on a clear night than immediately process it. @Demonperformer is right about the temperature, but it has nothing to do with being at the scope in the middle of the night. My point is, take the darks when it is convenient, not while stars are out to be grabbed.

Here's inspiration from a setup much similar to yours: https://www.astrokraai.nl/viewimages.php?id=264&cd=7&fbclid=IwAR0rYVe85SJFNnZAUvMVbPcEH3rWBMQWvvW84vOWAEm8zc4F4fHTeBZaDjc

 

[tooth_dr]

1 hour ago, Datalord said:

@Demonperformer is right about the temperature, but it has nothing to do with being at the scope in the middle of the night. My point is, take the darks when it is convenient, not while stars are out to be grabbed.

 

Nigella doesn't have a camera that can control the temperature of the sensor, so what you are proposing is not going to be possible.  That was my point about taking them during the day.  Nothing to do with light, everything to do with temperature.

[JamesF]

How about going out when it's cloudy and taking sets of darks whatever the temperature, thereby building up a library of darks at various temperatures over time?  Would that work?

James

[don4l]

Why do people think that the above image would benefit from darks? 

 

[Datalord]

1 minute ago, don4l said:

Why do people think that the above image would benefit from darks?

 

I don't think anyone does. We've just devolved into giving all sorts of different advice to a newcomer.

My point was, with the gear at hand, under bortle 6 skies, go for the short exposure route, which puts a lot less strain on the mount and can result in magnificent pictures when processing skills have been honed.

[Nigella Bryant]

38 minutes ago, Datalord said:

I don't think anyone does. We've just devolved into giving all sorts of different advice to a newcomer.

My point was, with the gear at hand, under bortle 6 skies, go for the short exposure route, which puts a lot less strain on the mount and can result in magnificent pictures when processing skills have been honed.

Thanks, it's very interesting. I think I'll go for shorter exposure but more of them next time I'm out under my light polluted skies. Would a 2inch Idas D2 filter be worth considering? Just to throw another spanner into the conversation. 

[Datalord]

28 minutes ago, Nigella Bryant said:

Thanks, it's very interesting. I think I'll go for shorter exposure but more of them next time I'm out under my light polluted skies. Would a 2inch Idas D2 filter be worth considering? Just to throw another spanner into the conversation. 

I don't know. I had LP filters for both my Canon 6D and later for the RASA under bortle 5, but I decided to remove them in both cases because it did more harm than good. That's my experience, but many others use them with success.

[Demonperformer]

5 hours ago, Datalord said:

I don't think anyone does. We've just devolved into giving all sorts of different advice to a newcomer.

My point was, with the gear at hand, under bortle 6 skies, go for the short exposure route, which puts a lot less strain on the mount and can result in magnificent pictures when processing skills have been honed.

Agreed, keep is simple.

There was an image on SGL some years back of the horsehead nebula consisting of 2000* 2s subs. Not the way I would choose to do it, but it can be done.

[tooth_dr]

7 hours ago, JamesF said:

How about going out when it's cloudy and taking sets of darks whatever the temperature, thereby building up a library of darks at various temperatures over time?  Would that work?

James

Not really, a guy on here did that and it didn’t work.  The temperature wouldn’t be stable in a DSLR, it could start ok then change. It is MUCH simpler ditching darks and dithering.