Astrophotography telescope+mount?

[william_swe1]

I have been using my 100d and my 55-250mm lens for deep sky imaging for some time now. (Getting pretty bad results). I am after a telescope to replace the lens. Celestron travel scope 70mm is the right one for me I think, and I think I will buy the sky watcher star adventurer to mount it on.

I have never owned a telescope setup before so there are a few things I don't know. How do I connect the telescope to the mount, are they even compatible? How do I connect my camera to the telescope? I have heard I need some kind of T-2 ring, every description I have seen is very unclear.

 

Celestron travel scope https://www.celestron.com/products/travel-scope-70-portable-telescope#

Sky watcher mount https://www.bhphotovideo.com/c/product/1092106-REG/sky_watcher_s20510_star_adventurer_motorized_mount.html

 

[happy-kat]

The star adventurer is a super idea. Why not first use it with the lens you already have. The travel scope will have a lot of chromatic aberration on bright stars.

[william_swe1]

I am pretty sure I will buy the star adventurer. But I am getting tired of my 55-250 lens. I feel limited because I can't get close enough to the object I am photographing.

[happy-kat]

What are you photographing?

[william_swe1]

Whatever I can! Most Jupiter. But I can't get a good enough image to see the belts. So I always settle for the moons. I have also tried photographing Orion nebula. But the nebula is only a few pixels wide

[ollypenrice]

'Getting close to the object you are photographing' has two meanings. Optically it means using a longer focal length. In terms of digital photography it means shooting at fewer arcseconds per pixel (so at a given focal length using smaller pixels.) Of course, you can do both and get even closer! But....

'the closer you get' the better your tracking has to be. The errors of your tracking will be magnified by the same amount as your magnification of detail.

Personally I very much doubt that a cheap achromatic telescope will beat a good second hand prime camera lens.

Olly

[Stub Mandrel]

A cheap solution to planetary photography with a light tracking mount like the star adventurer is probably a small Maksutov scope. Click on the FLO advert at the top of this page and search for 'maksutov'. A focal length of 1200mm plus a barlow is best for planetary, but because you use very short exposures accurate tracking isn't a big problem.

For DSOs you can do an awful lot between 100mm and 600mm focal length.

The orion nebula will look much bigger with the star adventurer and longer exposures, maybe ten times as wide!

[Alien 13]

I think you would find that the lens you have will perform better than the travelscope, I would agree with Neil that a small Mak will do wonders with lunar and planetary shots. 

Alan

[william_swe1]

What focal length should a lens at least have for decent deep sky imaging capabilities?

What about this one?https://www.ebay.com/p/Canon-FD-400mm-f-4-5-S-S-C-FD-Lens/111321869

[Alien 13]

Thats a difficult question the best option is to look at the resource section at the top of the page then astronomy tools, FOV calculator and try various focal lengths with different targets. I personally think things get realy interesting at 135 mm although there is a lot you can do with 50 mm or less, the maximum I would go for most objects is 400 mm unless its Lunar or Planetary.

Alan

[Davey-T]

4 minutes ago, william_swe1 said:

What focal length should a lens at least have for decent deep sky imaging capabilities?

You can't lump all DSOs together as they range from a few arcseconds " across " to arcminutes  " across "

So Heart Nebula around 3.00.00
Orion Nebula  around 1.30.00
Crescent Nebula around 0.20.00
Eskimo Nebula around 0.00.45

So you need from a short focal length wide field scope to a long focal length SCT to do them all justice

The SWSA is best suited to widefield.

Dave

[pete_l]

1 hour ago, william_swe1 said:

Whatever I can! Most Jupiter. But I can't get a good enough image to see the belts. So I always settle for the moons. I have also tried photographing Orion nebula. But the nebula is only a few pixels wide

Hang on, there's something odd happening here!
At 250mm focal length the Orion Nebula should be almost filling the frame. It should look something like this:

Image of Orion Nebula at 250mm

It will look "only a few pixels" if the exposure time of the photo was short. Then the image would only show the brightest patches. Try taking longer images: 10 sec, 30sec up to 2 minutes or so. And select Manual mode on the camera with a high-ish ISO setting, say 800.

[happy-kat]

Canon FD lenses will not reach infinity focus on the new EOS Canon DSLR unless it is the EOS-M series the mirrorless dslr (though I have never tried an FD lens personally on a EOS-M). However vintage m42 lenses with a clear none lens adapter (about £8) will reach infinity focus with a new Canon EOS dslr.

[william_swe1]

19 minutes ago, pete_l said:

Hang on, there's something odd happening here!
At 250mm focal length the Orion Nebula should be almost filling the frame. It should look something like this:

Image of Orion Nebula at 250mm

It will look "only a few pixels" if the exposure time of the photo was short. Then the image would only show the brightest patches. Try taking longer images: 10 sec, 30sec up to 2 minutes or so. And select Manual mode on the camera with a high-ish ISO setting, say 800.

Yeah! This is interesting. I must be doing something wrong. I will try photographing Orion nebula next time I have a chance.

The problem is that I must limit my exposure time because I don't own a tracker yet!

[ronin]

Is M42 around in Stockholm at present, amd surely Jupiter is below the horizon?

M42 is about a degree, so that makes an image of 4.5mm across so is not going to fill a sensor frame.

Planetary imaging is usually performed with a Mak or SCT and even then people add a barlow to increase the image size. So in a DSLR Jupiter is too small for deatail. In effect a different scope is required from tjat used for a DSO. Additionally for a planet it is usual that you take a video and stack and process thje best frames from the video. Again different to DSO imaging.

For a DSO (M42) you need a small(ish) scope and an equitorial mount. Consider something along the idea of a 70-72mm ED refractor. You attach the DSLR via a T-ring and a nose piece. Then you set the DSLR up to operate fully manual and set ISO, Exposure etc use an intervalometer to get a series of 20 to 30 second exposures then you stack these in DSS (Deep Sky Stacker).

If you are making the assumption that astrophotography is similar to photography then you have the wrong approach. It is somewhat totally different.

Any clubs that you can get to, as these tend to be a source of information?

The DSLR and lens will be reasonable for wide field shots, but owing to the focal length and maybe sensor size not really for specific DSO's. YTou will need a tracking mount of some variety, normal EQ or Skytracker type, but not Alt/Az. Also DSO images tend to be taken in RAW format then stacked, however DSS will stack the normal jpegs and that is a way to get initially familiar with the stacking process.

Try getting a wide field shot of Casseiopia or Cygnus, say 10 exposures of 20 seconds each then load these into DSS and practise with those. Darks are easy to add. Leave the DSLR setting as they are and get say 6 darks to add to the stack.

[Davey-T]

As we're discussing M42 this is a single 5 minute sub taken with SWSA, Canon 60Da and Canon 300mm lens to give you an idea of the FOV.

Dave

 

[newbie alert]

I think that m42 is only a few pixels wide because  you're using short subs and not using some sort of tracking mount..think the trapezium area is what's being imaged..get the SA and the subs can be minutes instead of seconds long..ive seen some amazing dso taken with 135mm lenses..

 

[ollypenrice]

7 minutes ago, newbie alert said:

I think that m42 is only a few pixels wide because  you're using short subs and not using some sort of tracking mount..think the trapezium area is what's being imaged..get the SA and the subs can be minutes instead of seconds long..ive seen some amazing dso taken with 135mm lenses..

 

I think this must be correct.

Olly