Jump to content

sgl_imaging_challenge_banner_31.thumb.jpg.b7a41d6a0fa4e315f57ea3e240acf140.jpg

General astrophotography questions


Recommended Posts

Hi all, 

I'm new to Astronomy having been gifted my first telescope a little over a month ago, it's safe to say; I'm hooked. 

With my 100mm aperture, 660mm focal length refractor scope with 2x Barlow and 10mm eyepiece in able to discern the rings of Saturn, the moons of Jupiter and pretty intricate images of the moon (during the rare cloudless night during November). 

I'm keen to continue into astrophotography as I learn to star-hop and I have so many questions the research is sucking up most of my free time! One question a Google search can't answer:

With magnification being easy to calculate for observation (focal length (x barlow lens) / eye piece length); how do you do the same for a DSLR camera? If I plug a DSLR straight into my scope with the specs above with a t-joint, how will I know the magnification? 

I'd also be interested to hear what you think is the best DSLR for a budding astrophotographer. Thinking of treating myself at Christmas (nothing bank breaking!) I've seen that the ir filter can be removed from most DSLRs from home however it would be great to get something pre-prepared. Perhaps ebay is my best bet? 

All the best and look forward to discussing further with you all!

Link to post
Share on other sites

I got my DSLR from cheap astrophotography online who was great.

Astrophotography covers so many areas, what are you interested in? Planets, wide field, galaxies, nebula etc

TBH probably best list out your equipment and let the good people here give much better advice than me

Edited by smashing
  • Like 1
Link to post
Share on other sites

Hello and welcome

I'm using a Canon 450D that was bought at 200$. I'm pleased with it (as a beginner).

About the magnification you can probably find some useful information here. Also, http://astronomy.tools/calculators/field_of_view/ has some nice features.

Clear skies,
Vlad

  • Like 2
Link to post
Share on other sites
45 minutes ago, SStanford said:

If I plug a DSLR straight into my scope with the specs above with a t-joint, how will I know the magnification? 

 

Hello and welcome, you will find answers to all your questions here I am sure..... however..... that question has some very interesting answers that I really don't understand. There is a very similar and recent thread on here that you may wish to search out, it has answered the question using words like radians, pixels etc, so my version of the answer to the question is that you don't get magnification from a camera, you are taking a picture. 🤔:D

Enjoy

  • Like 1
Link to post
Share on other sites
5 hours ago, smashing said:

I got my DSLR from cheap astrophotography online who was great.

Astrophotography covers so many areas, what are you interested in? Planets, wide field, galaxies, nebula etc

TBH probably best list out your equipment and let the good people here give much better advice than me

Thanks for this, any recommendations on DSLR to look out for? are the prices shown on cheap astrophotography typical?

I'm most interested in capturing galaxies and nebulae but it would be nice to capture pictures of the planets as I see them.

As an absolute novice, I have only the following equipment:

 - Celestron Inspire 100AZ refractor (100mm Aperture, 660mm focal length)

 - 10mm and 20mm Eyepieces (both Celestron)

 - 2x Barlow Lens (Celestron)

 - AltAz mount

In considering what next to buy to improve the setup my thinking was a DSLR (rather than a mount) so as to practice long exposures and get to grips with stacking/other AP software. 

4 hours ago, Anonymous Astronomer said:

Hello and welcome

I'm using a Canon 450D that was bought at 200$. I'm pleased with it (as a beginner).

About the magnification you can probably find some useful information here. Also, http://astronomy.tools/calculators/field_of_view/ has some nice features.

Clear skies,
Vlad

That sounds very reasonable! Did you modify the ir filter yourself or ship of for modification?

Where did you buy the camera at this price if you don't mind my asking?

4 hours ago, valleyman said:

You will get good 2nd hand Cameras here. I have used them for years and never been let down.

https://www.mpb.com/en-uk/

Stick to the Canon Brand  The 450D already mentioned comes in at under £90 which would be a good starting point before your wallet developed a Hugh hole in the bottom of it.

Sounds perfect; I'll be checking this out today.

 

4 hours ago, M40 said:

Hello and welcome, you will find answers to all your questions here I am sure..... however..... that question has some very interesting answers that I really don't understand. There is a very similar and recent thread on here that you may wish to search out, it has answered the question using words like radians, pixels etc, so my version of the answer to the question is that you don't get magnification from a camera, you are taking a picture. 🤔:D

Enjoy

 

4 hours ago, globular said:

Here is the thread on magnification that M40 was referring to:

 

Will also take the time to go through this thread.  Hopefully further answers here!

All the best.

Link to post
Share on other sites
18 minutes ago, SStanford said:

That sounds very reasonable! Did you modify the ir filter yourself or ship of for modification?

Where did you buy the camera at this price if you don't mind my asking?

Didn't modified the camera and I don't intend to do.

I bought the camera from a local store. I'm pretty sure you can find some decent gear online in UK. 

Link to post
Share on other sites

The most important piece of equipment before anything else should be the mount. Without a stable platform capable of tracking the night sky you wont be able to take long exposures. Before you decide to buy anything the first thing I recommend is research & the best way to start that is by buying this, it'll answer most questions you probably have plus a lot more  https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

Edited by nephilim
  • Like 2
Link to post
Share on other sites

And so it begins 🤣 who needs money anyway 😜  I tried afocal photography initially and couldn't get on with it, so I moved to a DSLR. I bought a used unmodified Canon EOS 100D primarily because of the weight of the body, its about as light as they come. It's an old unit now so there are likely to be newer and better models with a similar weight out there, have a look around and see what you can find. Enjoy 👍

Agree with nephilim, once you get into it you will realise how fast everything moves so it will take some practice on a manual mount but single shot pictures and getting the best out of your camera and telescope are part of things I enjoy about this hobby. A tracking mount will most certainly help in both observing and astrophotography 

Edited by M40
update
  • Like 1
Link to post
Share on other sites
46 minutes ago, M40 said:

And so it begins 🤣 who needs money anyway 😜  I tried afocal photography initially and couldn't get on with it, so I moved to a DSLR. I bought a used unmodified Canon EOS 100D primarily because of the weight of the body, its about as light as they come. It's an old unit now so there are likely to be newer and better models with a similar weight out there, have a look around and see what you can find. Enjoy 👍

Agree with nephilim, once you get into it you will realise how fast everything moves so it will take some practice on a manual mount but single shot pictures and getting the best out of your camera and telescope are part of things I enjoy about this hobby. A tracking mount will most certainly help in both observing and astrophotography 

 

48 minutes ago, nephilim said:

The most important piece of equipment before anything else should be the mount. Without a stable platform capable of tracking the night sky you wont be able to take long exposures. Before you decide to buy anything the first thing I recommend is research & the best way to start that is by buying this, it'll answer most questions you probably have plus a lot more  https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

I've just bought a second hand Canon EOS 450D for just under £110 so my mount will definitely be the next purchase.  I have a multitude of questions regarding mounts but will play with my camera and single shots before I start tracking!

Thanks for your help all. 

  • Like 2
Link to post
Share on other sites

It's great creating startrail images, did you get a camera lens as well with the camera.

It's is not impossible to take photos using a static mount, only the longer the focal length of the telescope/lens the shorter the exposure length before star trails show. Lots of 1 second exposures can reveal a globular cluster for example.

When you are considering mounts altaz mounts, even if motorised, move in tiny left right up down movements which keep the object in the field of view but don't follow the rotation. So exposure length capability is longer than a static mount but still limited before star trails show or smeering of nebula.

Edited by happy-kat
Typo
  • Like 1
Link to post
Share on other sites
17 minutes ago, happy-kat said:

It's great creating startrail images, did you get a camera lens as well with the camera.

It's is not impossible to take photos using a static mount, only the longer the focal length of the telescope/lens the shorter the exposure length before star trails show. Lots of 1 second exposures can reveal a globular cluster for example.

When you are considering mounts altaz mounts, even if motorised, move in tiny left right up down movements which keep the object in the field of view but don't follow the rotation. So exposure length capability is longer than a static mount but still limited before star trails show or smeering of nebula.

No lens with the camera unfortunately.

With regards to mount I'll be looking for tracking and potentially even GoTo but I don't really know what to expect in terms of price here! I don's suppose you know of any sites I can browse for mounts ahead of time? It would alos be great to know what kind of thing to look out for.  I'll be looking to take long expose shots; the ideal is to have a setup that will track the target and require little interference during the course of an evening.  

My next challenge will be finding software for the camera that, once the camera is plugged in via USB, acts as an Intervalometer (this is of course only really meaningful once I have a tracking mount but good to be prepared!)

I will definitely be experimenting with star trails whilst I only have an altaz.  

Question for those with a 450D or similar; do I need a memory card in the camera or will pictures be saved directly to the computer whilst plugged in with the USB? 

Link to post
Share on other sites

Unless you have software directing the camera I think you'll need a memory card.

You'll need to able to remote release the shutter, intervalometers are handy gadgets around 10GBP if not using a laptop etc.

 

Edited by happy-kat
typo
Link to post
Share on other sites

There are couple of things about mounts that you should pay attention to:

1. Load capacity.

You want to be at or below 60% stated visual capacity of the mount with all your gear. This is safe margin with even some small further upgrades. In any case - don't go over 2/3 to 3/4 (67%-75%), depending on mount quality, of stated visual carry capacity for imaging.

Counter weights usually don't count towards weight capacity of the mount - if it says for example that mount has 9Kg capacity for visual - you'll want to weigh all your kit - scope, rings, DSLR, any extensions (basically whole thing assembled as it will sit on mount) and make sure it is 5-6Kg max.

2. Periodic error. If you don't guide - this will be the thing that gives you the most issues and limits how long exposure you can have.

Just as a guideline - 30-40 arc seconds peak to peak is ok-ish P2P periodic error. Over about 40-45 arc seconds, we would call it large, and below 20 arc seconds - we would say it is relatively small (this is all in perspective of budget mounts, for premium mounts, small P2P periodic error is considered one below 2-3 arc seconds).

3. How well it guides. This is important if you guide.

Mount needs to be responsive - have low backlash, and have relatively smooth periodic error (it does not matter if it is relatively big as long as it is smooth) in order to guide good.

We can also speak in terms of budget:

up to £500 - very basic mounts, won't be really suitable for high performance work, mostly up to 3-4Kg of weight on them (AzGti, EQ3, EQ35)

£500-£800 - one step up, will handle up to 6-7Kg of gear and performance will be slightly better (EQ5)

£800-1500 - serious beginner / amateur mounts for astrophotography (HEQ5, EQ6, AZEQ5, AZEQ6) - will hold 10-15Kg of gear, guide good - usually recommended as starting point unless portability is important (they are heavy).

(I'm listing only Skywatcher mounts as examples, but you can compare price and put ExploreScientific, iOptron, Celestron and such mounts in any of above categories based on price an it will "fit" in principle).

 

Look at APT for Canon support - it allows you to operate Canon camera via computer and do all sorts of things needed for astrophotography.

https://www.astrophotography.app/

Edited by vlaiv
just naming apt without a link was not very useful
  • Like 1
Link to post
Share on other sites
2 hours ago, SStanford said:

No lens with the camera unfortunately.

With regards to mount I'll be looking for tracking and potentially even GoTo but I don't really know what to expect in terms of price here! I don's suppose you know of any sites I can browse for mounts ahead of time? It would alos be great to know what kind of thing to look out for.  I'll be looking to take long expose shots; the ideal is to have a setup that will track the target and require little interference during the course of an evening.  

My next challenge will be finding software for the camera that, once the camera is plugged in via USB, acts as an Intervalometer (this is of course only really meaningful once I have a tracking mount but good to be prepared!)

I will definitely be experimenting with star trails whilst I only have an altaz.  

Question for those with a 450D or similar; do I need a memory card in the camera or will pictures be saved directly to the computer whilst plugged in with the USB? 

I always use First Light Optics for my astro gear & have done for around 9yrs, they've always being reliable. https://www.firstlightoptics.com/

Link to post
Share on other sites
3 hours ago, vlaiv said:

There are couple of things about mounts that you should pay attention to:

1. Load capacity.

You want to be at or below 60% stated visual capacity of the mount with all your gear. This is safe margin with even some small further upgrades. In any case - don't go over 2/3 to 3/4 (67%-75%), depending on mount quality, of stated visual carry capacity for imaging.

Counter weights usually don't count towards weight capacity of the mount - if it says for example that mount has 9Kg capacity for visual - you'll want to weigh all your kit - scope, rings, DSLR, any extensions (basically whole thing assembled as it will sit on mount) and make sure it is 5-6Kg max.

2. Periodic error. If you don't guide - this will be the thing that gives you the most issues and limits how long exposure you can have.

Just as a guideline - 30-40 arc seconds peak to peak is ok-ish P2P periodic error. Over about 40-45 arc seconds, we would call it large, and below 20 arc seconds - we would say it is relatively small (this is all in perspective of budget mounts, for premium mounts, small P2P periodic error is considered one below 2-3 arc seconds).

3. How well it guides. This is important if you guide.

Mount needs to be responsive - have low backlash, and have relatively smooth periodic error (it does not matter if it is relatively big as long as it is smooth) in order to guide good.

We can also speak in terms of budget:

up to £500 - very basic mounts, won't be really suitable for high performance work, mostly up to 3-4Kg of weight on them (AzGti, EQ3, EQ35)

£500-£800 - one step up, will handle up to 6-7Kg of gear and performance will be slightly better (EQ5)

£800-1500 - serious beginner / amateur mounts for astrophotography (HEQ5, EQ6, AZEQ5, AZEQ6) - will hold 10-15Kg of gear, guide good - usually recommended as starting point unless portability is important (they are heavy).

(I'm listing only Skywatcher mounts as examples, but you can compare price and put ExploreScientific, iOptron, Celestron and such mounts in any of above categories based on price an it will "fit" in principle).

 

Look at APT for Canon support - it allows you to operate Canon camera via computer and do all sorts of things needed for astrophotography.

https://www.astrophotography.app/

APT looks perfect, can see from the user manual that saves directly to connected computer so that works for the time being. 

I'll be playing around with this, trying a few sort exposure stacks and seeing what I can achieve with a limited setup before splashing out on a meaningful mount. 

Does anyone have an opinion on light pollution filters? The ones I'm looking at are at the £100 and I'm curious if they really are value for money... 

All the best. 

Link to post
Share on other sites
13 minutes ago, SStanford said:

Does anyone have an opinion on light pollution filters? The ones I'm looking at are at the £100 and I'm curious if they really are value for money... 

I think that they sometimes hurt more than help, and sometimes help greatly.

It depends on the type of the filter and type target and level of light pollution that you are facing. I'll try to give a few recommendations.

UHC is poor man's narrowband / dual / tri / quad band filter and I think it is worth having. It will be very good on emission type nebulae - which means Ha regions, regular emission type nebulae like M42 but also planetary nebulae. It will cut most of light pollution and is good in both strong LP (Bortle 7-9), medium LP (bortle 5-7) and light levels of LP (Bortle 3-5).

It will create strong color balance issues for stars, but you can treat your images as narrowband and just ignore star color / process image in a way that deals with this. Don't use it on broad band targets like galaxies, star clusters and reflection nebulae.

I would avoid CLS type LP filters - they cut too much of spectrum and cause color balance issues.

For general purpose LPS filter - you really want a good filter. I personally use Hutech IDAS LPS P2 filter. However, I recommend using one only in strong / medium LP levels. If you image from Bortle 5 and below - don't use one.

In my experience, using IDAS LPS P2 makes considerable difference. It is equivalent of replacing my Bortle 7/8 (SQM 18-18.5) for Bortle 5 skies (SQM 19) - lowering SQM by about 1-1.5 mags and it does not have much impact on target. Color balance is good with it.

If you are going to use achromatic refractor as a telescope of choice - then you might want to look at this filter:

https://www.firstlightoptics.com/achromat-semi-apo-filters/baader-contrast-booster-filter.html

It will handle some issues with blue star bloat and provide some filtration on main LP lines (sodium lines). It is also less expensive option. Pay attention to use UV/IR cut filter as well (if your camera does not have one already).

  • Like 1
Link to post
Share on other sites
On 18/11/2020 at 20:36, SStanford said:

Does anyone have an opinion on light pollution filters? The ones I'm looking at are at the £100 and I'm curious if they really are value for money...

If the location in your profile is where you're going to image from, a LPS filter is going to help.

Hutech IDAS LPS filters are quite popular. There are many different types and you should pick one based on what kind of street lights are installed in your vicinity. The P2 mentioned previously works very well against Sodium lights. If the street lamps are WLED based, you will want the D2. I used to have a D2 before my recent house move (I live in a Bortle 5 area so a LPS filter isn't generally required. But there was a closeby LED footpath lamp near my old house so I had no choice). It worked ok but did cause pretty serious colour balancing issues in broadband targets. It was quite evident in my M31 shot (link in my sig. You can compare it to the ones taken without any filters by other ppl to see the issues).

BTW I'd strongly recommend getting your DSLR modded for astro-imaging. Losing out on the Ha band is a big disadvantage for many targets. My 600D was modded by astronomiser: http://www.astronomiser.co.uk/

With your 450D you should stick to ISO400 (or 800) for best dynamic range in your ap captures. You can read up the reasons behind this here: http://dslr-astrophotography.com/iso-values-canon-cameras/

 

Edited by KP82
  • Like 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.