22
$\begingroup$

Hi built my own newtonian telescope for the first time. Up until that point I had never used a telescope.

Can you please look at the photos attached and tell me if this is what Mars should look like as I'm disappointed somewhat.

Specs are as follows:

  • Picture taken with smartphone through the eyepiece and no filters were used or edited.
  • TMB Planetary Series 2.5 mm 3.2 mm eyepieces
  • 10" (25 cm) Newtonian with f = 1470 mm

Mars with a TMB 2.5MM and 3.2mm lens (cropped)

uncropped original

Improve this question
$\endgroup$
5
  • 4
    $\begingroup$ Congratulations on building a telescope! I've made some edits to make the formatting of your information clearer, but I'm not 100% sure I've got your diameter and focal length correct. Can you have a look? Thanks! $\endgroup$
    – uhoh
    Commented Nov 13, 2020 at 17:52
  • 8
    $\begingroup$ Now, how does it look to your eyes when you look through the eyepiece? Is it too bright? If so then keep watching the planet and your eyes will adjust and the contrast will improve. Is it too blurry? If so then back off the magnification a bit until it's not blurry any more. A smaller crisper image is much better than a larger blurry image - your eyes will be able to pick out tiny details in a tiny image with time and practice. $\endgroup$
    – Aaron F
    Commented Nov 13, 2020 at 18:03
  • 8
    $\begingroup$ Aaron. That is a complete answer! You can copy paste your comments as an answer. $\endgroup$
    – James K
    Commented Nov 13, 2020 at 18:05
  • 1
    $\begingroup$ @JamesK :-D you're right! I thought "I have to pop out and don't have time for a full answer, so will 'just write a quick comment'..." ... two quick comments later...! I shall do as you suggest now I'm back :-) $\endgroup$
    – Aaron F
    Commented Nov 13, 2020 at 20:49
  • 7
    $\begingroup$ I'd vote up just for the OP trying the lost art of building a telescope. Somehow it is unfair that physics does not reward the OP better for their effort. :-) $\endgroup$
    – StephenG - Help Ukraine
    Commented Nov 13, 2020 at 22:28

2 Answers 2

Reset to default
38
$\begingroup$

(Much of this echoes what antlersoft says in their answer)

For a phone photo through the eyepiece that looks about right to me! The size... the brightness... both are as I expect.

What you could try is to use the manual mode of your phone's camera and set the ISO down to minimum (100) and the shutter speed down to something like 1/60s.

Take a few shots, pick the best one, and make a zoomed+cropped version.

You should be able to see a point of white on the south pole and a hint of dark patches.

If the seeing's bad then you'll get awful results no matter what, so wait until the view is nice and crisp.

Now, when you look through the eyepiece, how does it look to your eyes?

Is it too bright? If so then keep watching the planet and your eyes will adjust and the contrast will improve.

Is it too blurry? If so then back off the magnification a bit until it's not blurry any more. A smaller crisp image is much better than a larger blurry image - your eyes will be able to pick out small details in a tiny image with time and practice.

Here's a lucky snap I got a few weeks ago: Mars 16 October 2020

And here's a zoomed and cropped version: Mars 16 October 2020 zoomed

And here's one from one minute beforehand with automatic camera settings: Mars 16 October 2020 overexposed

These were taken through the eyepiece of a 10" F/5 Dobsonian - very similar to yours. (I can't remember which eyepiece I had in at the time, I'm afraid! I think it was a 4.5mm but it could have been an 8.8mm with 3x Barlow lens, or even a zoom lens plus the 3x Barlow...all I do remember is that the seeing was exceptionally good that night and I was making the most of it!)

The good one was ISO 100 and an exposure time of 1/60s. The bad one was ISO 100 and an exposure time of 1/17s.

Hopefully these photos demonstrate that everything has to come together to be able to get a halfway decent photo: the seeing, the collimation, a steady hand, the camera settings... :-)

Improve this answer
$\endgroup$
3
  • 5
    $\begingroup$ Guys thank you so much for all your answers and suggestions. Very helpful and appreciated.❤ $\endgroup$
    – Edd
    Commented Nov 13, 2020 at 21:34
  • 5
    $\begingroup$ What a great answer. This is stackexchange at its best. $\endgroup$
    – user15381
    Commented Nov 14, 2020 at 20:08
  • 2
    $\begingroup$ Seeing the first two photos (before the one with the automatic camera settings) makes Mars feel so much more real than normal. Usually you either see it on TV or online, or you look up into the sky and see a tiny dot with a single color, or you take other people's word for it, or something. But seeing an average Joe picture - not a fancy observatory one or something - from somebody's backyard, which actually shows different colors for different regions of the planet and so on - and with a raw, "lo-fi" look, without fancy editing or perfecting - is incredible and makes it feel much more real. $\endgroup$
    – Panzercrisis
    Commented Nov 16, 2020 at 17:58
20
$\begingroup$

It's very difficult to get any kind of picture just holding your phone up to the eyepiece, and the picture you posted is overexposed and probably motion-smeared, but other than that it's what you'd expect.

Planetary observation is a learned skill; planetary detail is usually very low contrast. Mars is a small target and you have to use lots of magnification, which makes it very vulnerable to "seeing", the constantly shifting distortion caused by air moving in the telescopes line of sight. Good observers can mentally capture the details that show up in moments of "good seeing." The best ground-based images are doing sort of the same thing; they attach a video camera to the telescope and then select the clearest frames, using software to stack them together to bring out detail and contrast.

Improve this answer
$\endgroup$
1
  • 1
    $\begingroup$ I'd echo that, and I'd also add that with the arrangement described- multiple air/glass interfaces in the eyepiece, a marginally-clean camera window on the 'phone, and multiple air/glass interfaces in the 'phone's camera- there's going to be an inherent degradation of contrast. That's why cameras are normally mounted at the prime focus of the optical system, with any interposed diagonal mirror front-silvered... and why it's so important that the accessibility of this is considered in the construction or purchase of a telescope. $\endgroup$
    – Mark Morgan Lloyd
    Commented Nov 15, 2020 at 19:59

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .