do I need to calibrate my telescope?

[bduffez]

Hi. I recently received a Celestron aeromaster 130 as a gift and I am preparing to use it. I already have watched the moon and liked it.

I wanted to check image quality during the day. I pointed the telescope at a neighbor's bush about 200ft away. The image appeared smeared and I could not get something sharp.

Do I need to perform some calibration to improve image quality? I have added a photo of said bush. All pictures taken with my phone through the eyepiece (except for the 3rd one of course). The pictures obtained are an accurate representation of what is seen with the naked eye through the eyepiece

[Richard N]

Hi there. It’s entirely possible that the bush is too close for the telescope to come to focus on. I would try on something more distant. If it’s working on the Moon, it’s probably fine. The Aeromaster is (I suspect) a telescope of the Bird-jones design. The reviews suggest that the optics are not the best. But I’m sure you can still have some fun with it. 

Edited April 9 by Richard N

[Cornelius Varley]

2 hours ago, Richard N said:

The Aeromaster is (I suspect) a telescope of the Bird-jones design

No, the Astromaster 130 is a standard Newtonian reflector (130/650) and possibly has a spherical primary mirror, although more likely to be parabolic.

[Richard N]

1 hour ago, Cornelius Varley said:

No, the Astromaster 130 is a standard Newtonian reflector (130/650) and possibly has a spherical primary mirror, although more likely to be parabolic.

That’s good to hear!

[Naughty Neal]

Select an object farther  away to focus on , the bush may not be with in the focal range of the telescope and simply to close.

Remember these telescopes are designed to have a long distance focal range and not a near  close focal range of bird or  general use spotting scopes. 

Edited April 9 by Naughty Neal

[ollypenrice]

The roof behind the bushes is pretty sharp. So, interestingly, are the fence and some other items in front of  the bushes. The obvious conclusion would be that the unsupported branches of the bushes were moving in the breeze...

Olly

[bduffez]

First, thanks all for the time taken to read & provide insights. Much appreciated.

I tried again this morning in the same spot and could not reproduce the smearing I saw yesterday.
I could get some sharpness in the middle of the smearing so I had assumed that the distance was enough.

I tried again with a different target and I have two focus pictures: this is an avocado tree about 300-500ft away and in the background is the ocean/coast which is about 5-8 miles away
The 1st image is a focus on the avocado tree, the second is the background.

The tree image isn't as good as what I had in the eyepiece (20mm btw), it looked better in real. It was a bit sharper than what we see on the first picture.
I don't see the smearing I had yesterday on the pink bush. I don't know what was up with that.

Now focus on the background: I could never get the coast/ocean to be sharper than what we see here, which is an accurate depiction of what I saw in the eyepiece.
This was taken at about 7am in southern California, about 50F and the sun had just risen. I suspect there was no refraction from heat at that time.

 

So bottom line is my scope does not need any calibration (since the smearing is gone) and the optics are probably what they are...
Out of curiosity, what is the limiting factor here? Large mirror, small mirror or eyepiece?

Thanks again

[Richard N]

59 minutes ago, bduffez said:

F

So bottom line is my scope does not need any calibration (since the smearing is gone) and the optics are probably what they are...
Out of curiosity, what is the limiting factor here? Large mirror, small mirror or eyepiece?

Thanks again

A question. Are you running out of adjustment at all? By which I mean is the focusser (knob you are turning) hitting the end stop?  The coast should look better but with a photo taken on a mobile phone (I assume). a blurry photo is perhaps as good as you can do. The advocado tree looks to be very close to being in focus to me. Perhaps your best bet now is to see if you can focus on a bright star. The point of focus should be similar to where the shoreline is nearly in focus. The objective with a star is to get it to be a small circular point of light, not a blurry ball. With regard to your other question, all things being equal, the eyepiece is probably the weakest link.

Edited April 9 by Richard N

[bduffez]

Here is a video where I go from > infinity down to closest and back to > infinity

We can see the beach going to a sharpness maximum at about 00:04, then the trees at 00:10, then the tree again at 00:20 and the beach again at 00:27.

It feels like there is a position of the knob that would provide focus for both (e.g. "infinity" if 5-8 miles is enough, and the closer tree) however I never reach a good crisp image.
So to answer your question, I should reach focus before I reach either end of the focusser.

Is it because of the eyepiece?
This time I used the 10mm one.

It is indeed filmed with my phone with a 2x magnification (pixel 6).