Not seeing as much as expected

Got a beginners' question? No matter how elementary, our friendly forum community and magazine writers will answer it.

Not seeing as much as expected

Postby nruk » Tue May 31, 2016 2:08 pm

Just bought a telescope for the first time

SkyWatcher Startravel 120mm AZ3 Refractor Telescope with Eyepieces Supplied (1.25"): 10mm & 25mm

All set up last night and managed to find what I am sure were Jupiter, Mars and Saturn. I admit my expectations were probably a bit high and I expected to see huge planets in my viewfinder but things were smaller than I imagined. It was out of a bedroom window which I know is far from ideal before you all tell me but its only day one and tonight my 4 year old will be expecting to see spaceships etc!!

Based on the above, what should my realistic expectations be? Look on the internet and already get the impression I should be buying Barlow lenses.

Go easy on me!! Everybody started somewhere :)
nruk
 
Posts: 2
Joined: Tue May 31, 2016 1:45 pm

Re: Not seeing as much as expected

Postby Aratus » Tue May 31, 2016 4:00 pm

It is unfortunate that people see images taken with large telescopes, or space probes, and expect to see similar things with an amateur telescope! :( However, theoretically your 5" refractor could yield magnifications of 200x or even 250x. :) (Some people believe that can be pushed even further.) Your 10mm eyepiece will give you a magnification of only 600/10 = 60x, so I think it is safe to say that your telescope is being under utilised!

A x2 barlow will double the magnification of an eyepiece. An eyepiece with a smaller focal length will also give you increased magnification. For instance a 4mm eyepiece would give you 600/4 = 150x. A 6mm eyepiece with a x2 barlow will give you (600/6)x2 = 200x, which I believe would give you the best image under normal conditions. There are a large number of other permutations! I think a barlow is a good place to start.

(btw - the '600' figure above is the 'focal length' of your telescope)

If you are going to use larger magnifications, then you need good 'seeing' conditions. The warm air coming out of a bedroom window will not help you in that respect! :D I think you already realise that!

Keep with it, and enjoy exploring the night sky together.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 838
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Not seeing as much as expected

Postby nruk » Tue Jun 07, 2016 12:56 pm

Many Thanks for that reply. Its really helpful knowing how the magnifications work and what I am working with.

For the immediate though, going to stick with what I have got to see what I can find. Viewing last night was excellent with Jupiter and Saturn easy to pick out, even for a beginner.

Waiting for the moon to magically appear for the first time since I set up my telescope. I do have a moon filter so really looking forward to that!!
nruk
 
Posts: 2
Joined: Tue May 31, 2016 1:45 pm

Re: Not seeing as much as expected

Postby Supercooper » Mon Jun 13, 2016 10:32 pm

HI,

I agree with Aratus. You'll need magnifications somewhere between 120x and 250x to see the planetary details with any clarity, but you must always also use the eyepiece that gives you the best view.

With my 127mm f9 refractor I can use 352x on really still nights (1145mm / 6.5mm = 352), but more often than not I'm getting just as nice an image at 230x ({1145mm / 10mm} x 2 [Barlow ] = 230x) The focal ratio of an optical system is found by dividing the diameter of the object glass or mirror by its focal length 1145mm focal length divided by 127mm diameter = f9.

A Barlow is a good place to start because the eye-relief remains the same as the longer focal length eyepiece (Eye relief is the distance of the eye from the lens of the eyepiece, which can get down to a millimtre or so in very short, older configuration (A Herschellian [H4mm] for example.) short focal length designs). Very short focal length eyepieces have much smaller eye relief and can be tricky to use.

Always have a look at different magnifications and select the one which gives the view you get the best result with (on any particular night).

Seeing detail on the planets is something that comes with experience and focusing! With Jupiter and Saturn it's handy to focus carefully on one of its moons then look at the planet. If at first you can't see much detail, stick with it and you'll see more and more as better seeing nights and experience build up ;o)

Cheers, Barry
________________________________________________________________________________________
For My FREE Telescope Help Website: http://supercooper.jimdo.com/

Using fab Helios f8 150mm Achromatic Refractor on SkyWatcher EQ5 - enjoing the views!
Supercooper
 
Posts: 119
Joined: Sun Feb 14, 2016 10:14 am

Re: Not seeing as much as expected

Postby Aratus » Fri Jun 17, 2016 6:20 pm

It is strange that the OP's telescope eyepieces that came with the telescope grossly underuse the telescopes capabilities. At one time they would often include combinations that were quite unusable. The pendulum seems to be swinging the other way now.

Eye relief is a big problem for eyepieces with short focal length. I remember even 20 years ago a 4mm was hard to use. Now I am that much older my eyes really can't cope with them any more. Thank goodness that an 8mm and a barlow give the same magnification, and much better eye relief.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 838
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Not seeing as much as expected

Postby Supercooper » Thu Jun 23, 2016 9:22 am

How is it coming along, nruk?

Did you get a Barlow or another eyepiece?

I had one of these telescopes and the images were very good. So, don't go worrying that your telescope isn't any good... See pic.
Saturn is a wonder at the moment as the rings are fully open. Which makes glimpsing the Cassini Division more likely.
Jupiter is nearly as far from earth as it gets, so the fact that it can still show a wealth of detail is encouraging for the beginner. At opposition (When it is due south at midnight) Jupiter will be about 50% larger in the eyepiece!
This is a good opposition for Mars, I'm afraid, quite a disappointing little body.

Keep us informed buddy.

Cheers, and good seeing, Barry ;o)
Attachments
StarTravel102 (19 Small).JPG
My StarTravel 102
StarTravel102 (19 Small).JPG (83.69 KiB) Viewed 2473 times
________________________________________________________________________________________
For My FREE Telescope Help Website: http://supercooper.jimdo.com/

Using fab Helios f8 150mm Achromatic Refractor on SkyWatcher EQ5 - enjoing the views!
Supercooper
 
Posts: 119
Joined: Sun Feb 14, 2016 10:14 am

Re: Not seeing as much as expected

Postby smanitta89 » Thu Aug 11, 2016 11:27 am

I have the Skyprodigy Celestron 130 Computerized telescope and I am new to astronomy. I require someone to help me with using this telescope to its full potential. If it means I need better eyepieces then the 9mm and 25mm to see the clearest images then I will certainly buy them. If there is anyone who can help me with this as I am only at the learning beginner level then I would be most grateful. thank you.
smanitta89
 
Posts: 1
Joined: Thu Aug 11, 2016 9:56 am

Re: Not seeing as much as expected

Postby Aratus » Sat Aug 13, 2016 12:05 pm

Why are you dissatified with your results so far?
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 838
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Not seeing as much as expected

Postby The Man with the Corrugated Iron Roof » Sun Aug 21, 2016 12:11 am

Aratus wrote:It is unfortunate that people see images taken with large telescopes, or space probes, and expect to see similar things with an amateur telescope! :( However, theoretically your 5" refractor could yield magnifications of 200x or even 250x. :) (Some people believe that can be pushed even further.) Your 10mm eyepiece will give you a magnification of only 600/10 = 60x, so I think it is safe to say that your telescope is being under utilised!

A x2 barlow will double the magnification of an eyepiece. An eyepiece with a smaller focal length will also give you increased magnification. For instance a 4mm eyepiece would give you 600/4 = 150x. A 6mm eyepiece with a x2 barlow will give you (600/6)x2 = 200x, which I believe would give you the best image under normal conditions. There are a large number of other permutations! I think a barlow is a good place to start.

(btw - the '600' figure above is the 'focal length' of your telescope)

If you are going to use larger magnifications, then you need good 'seeing' conditions. The warm air coming out of a bedroom window will not help you in that respect! :D I think you already realise that!

Keep with it, and enjoy exploring the night sky together.


Yes, I'm the noisy one that believes in pushing magnification but only for bright objects using Maksutovs and ED/APO refractors.

I once saw Venus at 600x with a 60mm refractor and it looked like a comet!
How can I be one with the universe when we don't know what 96% of it is.

My website: http://www.philippughastronomer.com/

My blog: http://sungazer127mak.blogspot.com/

Photos: https://www.flickr.com/photos/philippughastronomer/
The Man with the Corrugated Iron Roof
 
Posts: 487
Joined: Sat Nov 23, 2013 1:53 pm
Location: Wiltshire but can be just about anywhere up to 41 000 feet

Re: Not seeing as much as expected

Postby Aratus » Sun Aug 21, 2016 1:52 pm

I try not to be dogmatic. While sticking to the 'theoretical', I'm happy to keep the door open to your opinion/practice on the subject. I'll leave it to you elaborate though. :D

What we can agree on is it never does any harm to push the magnification until seeing conditions make the image worse. There are very occasionally times of incredibly good seeing and it would be a pity to miss those. This summer I had one example of such conditions, and I was able to catch details on Mars I didn't really expect. What I want to avoid is to give anyone the impression that buying barlows and low focal length eyepieces is automatically the answer to getting a better view. It will far more often than not - disappoint.

In this particular case the eyepieces that came with the telescope are yielding much less magnification than the theoretical maximum, and certainly fall way short of your own limits. A far cry from the old days when manufacturers were quite happy to announce magnifications which would give such dark images that it was impossible to see anything, even looking at bright objects. :!:
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 838
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Next

Return to Ask a silly (astronomy) question

Who is online

Users browsing this forum: No registered users and 1 guest