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How would you take a picture of/frame the following objects: Heart Nebula, M33, M43, M3, M13, M51, M63?

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#1 thornhale

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Posted 12 April 2021 - 12:18 AM

The purpose of this question is 2-fold.

 

1.) The list of objects above is chosen on purpose to be very varied. The heart nebula is very wide and faint, M33 (Andromeda's Galaxy) is 6 times the size of the moon. On the other hand, M3, and M13 and more tight globular clusters. For visual astronomy it's said that one needs at least a 200mm telescope to resolve the stars. Lastly, we have M51, and M63 which are galaxies that become smaller and smaller with distance.  As a beginner, I would like to learn from more experienced people how they would frame the objects above, i.e.: learn what equipment they would use so I can take better pictures as well.

 

2.) The other underlying question I am trying to answer for myself is with that large range of objects (in size and apparent magnitude): What is the minimal number of OTAs needed to cover such a large range? I am asking because initially, I naively thought that I could use my 6" F5 Newtonian to cover many use cases such as visual observations of the above objects, but also astrophotography of objects in the case above. What I am learning though is that this telescope has certain limits in terms of framing. That OTA with my m43 camera limits are M33 which only mostly fits in the FOV. On the other hand, M51 is a nice object and the 6" Newtonian can capture that but it's starting to look smallish. Other smaller galaxies probably need a longer focal range. At this time, I am considering getting another scope something between 70-80mm F5-6. This purchase would enable me to fully capture larger objects. On the other hand, refractors like that are also much more portable (as in being able to take it on an airplane) compared to a 6" Newtonian which is still portable but only car road trip portable. In essence, I want to go as minimalist as possible in terms of OTA acquisition. For instance, my thinking is that if I want to go even wider, instead of purchasing another telescope, a camera telelens could cover that aspects, so I would purchase that instead of a single-purpose OTA. I hope that purchasing the 6" Newtonian has not been a misstep already to get to that goal (but I digress).

 

 



#2 bobzeq25

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Posted 12 April 2021 - 12:54 AM

The key thing to know.

 

If your goal is to image small targets with a big scope, you'll reach it faster/better/cheaper if you start with a small scope and big targets.  Among other things, they make diagnosing issues easier.

 

There will be issues.  <smile>

 

The next most important thing to know.  There's a considerable difference between the best equipment to learn on, and the best for an experienced imager to use.  A Formula One car can go around a track real fast, but it's not something you'd want to learn to drive with.


Edited by bobzeq25, 12 April 2021 - 01:15 AM.


#3 dswtan

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Posted 12 April 2021 - 02:15 AM

A lot depends on personal preference as you get more experienced, but in *my* experience, and with typical (mainstream) current DSO cameras, a <500mm f/l refractor is good for the larger objects (some mosaics will still be required to capture whole targets and their context -- relatively easy with modern software), and a >1000mm f/l reflector (or refractor if you have the funds and mount) is best for the common smaller targets. 

 

Another key variable to consider is the pixel density of the camera(s) you select. Personally between my 80mm refractor (448mm reduced) and 8" RC (1125mm reduced), plus an ASI1600 + ASI183, I have all the *common* objects (like you listed) covered -- again, with some mosaics for the larger. Others might choose a larger chip like an APS-C DSLR or one of the available DSO cameras (they get pricey quickly, as do the filters if you go mono) to get a wider view. 

BTW, other key variables that affect the smaller objects are the quality of your mount and local seeing. 

 

But bottom line, 2 should do it. Depending ultimately on personal taste.

 

Your 6" is a fine compromise in many respects, but it's also awkwardly in the middle. You'd probably enjoy a wider scope (especially to learn on like Bob so often highlights), and a longer scope for the smaller stuff. You can confirm with the available FOV simulators such as Telescopius or https://astronomy.to.../field_of_view/

 

The 80mm you're considering would be a sensible purchase IMO. And great to learn on like Bob says. Yes you can alternatively use a telephoto lens, but focusing can get tricky and the cost goes up for quality. It would be portable though. This is where it all gets so personal...

 

FWIW, I have other scopes in my signature for other purposes, like lunar and planetary (and solar). I have some duplication too, but such is life -- I've been doing this a long time! It also gives me more precise framing options and is fun to play. :-) 


Edited by dswtan, 12 April 2021 - 07:42 PM.


#4 sg6

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Posted 12 April 2021 - 02:57 AM

Framing an object can be as "simple" as take the image with 2x or 3x the size of the object. That way you have the object and sufficent of the universe around it for the object to stand out.

 

Becomes less easy for a long thin object. You have to work at for for that. Means you need to know how to work out the maximum dimension of the object on the camera sensor. And consequencly know the sensor dimensions.

 

How many exposures rather simply depends on the intrinsic brightness of the object. I suppose "number" also means how good your setup and tracking is since it is more exposure time collected not a simple "number". Always remember that the purpose is for a decent image, not to get your name on the list for longest single exposure of the day.

 

Next is sort of obvious: How many scopes do you have?

Ever seen photographers at an event of some sort? They take 5 or 6 high quality lens along, and all different. Many APer's pick one lens (we call it a scope) and expect it to do everything. Not a chance!

 

Another is a good DSLR lens will cost $4000 to $6000 (believe me they do), then an astronomer tries to use the least expensive piece of optics they "think" they can get by with. Usually it is a bit of a failure. Sticking the words "APO" on a scope does not actually mean it is an APO, just that the manufacturer has decided to call it such. And then get money from deluded imagers who look no further then what they are told.

 

Your first images should I suggest be short and simple, and preferably easy. Forget guiding, forget many apps. Learn what it is that you have to do. Since my first days of software I have only and always looked upon software as a tool to help me. To me all software - call it whatever you like - is simply a tool for me to use. It is how I use it that matters.

 

Forget all these spreadsheets, when you are outside in the dark and cold avoiding the bears, rattle snakes and skunks you will likely not have time for a spreadsheet.

 

Have an idea before you go out. Do you have any idea how useful applying some thought is beforehand ? Seems absent in most cases, but is useful. Also means you can have a backup plan, if required.



#5 happylimpet

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Posted 12 April 2021 - 03:03 AM

many objects have fascinating fine detail at scales so small you cant fit the whole object in and get the tiniest details, for example M31 or even M42. So theres no hard and fast rules.

 

And when it comes to wide field compositions, this is where the creative artistic element creeps in. The best images are the surprising ones.



#6 the Elf

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Posted 12 April 2021 - 03:53 AM

 

What is the minimal number of OTAs needed to cover such a large range?

I recommend a factor of roughly 2.5 between your OTAs' focal lenghts, not more than three. My list is 180mm, 420mm, 1100mm, her is the family photo:

 

Family.JPG

 

 

So this is 180 x 2.3 --> 420 x 2.6 --> 1100. This covers everything from the cosmic question mark or Heart and Soul to Ring in Lyra. See my gallery for examples:

https://www.elf-of-l...de/Gallery.html


  • thornhale, UrsaMaatRa, Mike in Rancho and 1 other like this

#7 thornhale

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Posted 13 April 2021 - 12:26 AM

I recommend a factor of roughly 2.5 between your OTAs' focal lenghts, not more than three. My list is 180mm, 420mm, 1100mm, her is the family photo:

 

Family.JPG

 

 

So this is 180 x 2.3 --> 420 x 2.6 --> 1100. This covers everything from the cosmic question mark or Heart and Soul to Ring in Lyra. See my gallery for examples:

https://www.elf-of-l...de/Gallery.html

What's that Askar OTA in the middle?



#8 the Elf

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Posted 13 April 2021 - 12:40 AM

https://agenaastro.c...ope-fma180.html

 

That is a small but otherwise regular triplet (semi) APO that comes with a matching flattening reducer and a helical focuser. Camera side is a T-thread (M42x0.75), front side takes 2'' filters. It comes with extra extension tubes if you want to use it at native focal length or for visual. It has minor issues with blue halos that can be corrected in processing or by the Baader Semi-APO filter. It outperforms any lens I have tried so far. Here is my review:

 

https://www.elf-of-l...Art_FMA180.html




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