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Not having a pleasant experience with my reflector

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#1 Nikolai

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Posted 13 July 2020 - 07:29 PM

Hello folks.
I'm new to this hobby. Before finding this site and reading up on the new hobby, I picked up a refractor from ES on sale. The aluminium fork mount was terrible, so after looking around at the prices for a decent mount I decided to go with a cheap ES Explore One reflector. I have to say the mount is great compared to the aluminium one. It had some play to it but tightening one nut took care of most of it. So now I have a decent (I can only compare it to the other one I have) mount and two cheap telescopes.
Yesterday afternoon I noticed the moon was up and decided to take a look. It was the first time that I used my reflector. The view would have been great if not for the spider and the secondary being visible ever so slightly, that ruined the whole experience. I added a barlow and the spider disappeared. I guess what I want to know is if anyone else had this issue and is there a different way to solve this. (Other than getting an expensive telescope) The telescope is Explore One, 114mm Aurora II, f/l 500mm. I did spend a few days learning how to collimate it prior to using it. I think I did everything correctly but could that be related? Or is it because the telescope is so fast? Or is it simply because it is so cheap?

#2 bobzeq25

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Posted 13 July 2020 - 07:35 PM

Hello folks.
I'm new to this hobby. Before finding this site and reading up on the new hobby, I picked up a refractor from ES on sale. The aluminium fork mount was terrible, so after looking around at the prices for a decent mount I decided to go with a cheap ES Explore One reflector. I have to say the mount is great compared to the aluminium one. It had some play to it but tightening one nut took care of most of it. So now I have a decent (I can only compare it to the other one I have) mount and two cheap telescopes.
Yesterday afternoon I noticed the moon was up and decided to take a look. It was the first time that I used my reflector. The view would have been great if not for the spider and the secondary being visible ever so slightly, that ruined the whole experience. I added a barlow and the spider disappeared. I guess what I want to know is if anyone else had this issue and is there a different way to solve this. (Other than getting an expensive telescope) The telescope is Explore One, 114mm Aurora II, f/l 500mm. I did spend a few days learning how to collimate it prior to using it. I think I did everything correctly but could that be related? Or is it because the telescope is so fast? Or is it simply because it is so cheap?

Cheap is definitely an issue.  But some people just prefer refractor stars.  Nothing wrong with that.



#3 Chris Y

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Posted 13 July 2020 - 07:40 PM

Hello folks.
I'm new to this hobby. Before finding this site and reading up on the new hobby, I picked up a refractor from ES on sale. The aluminium fork mount was terrible, so after looking around at the prices for a decent mount I decided to go with a cheap ES Explore One reflector. I have to say the mount is great compared to the aluminium one. It had some play to it but tightening one nut took care of most of it. So now I have a decent (I can only compare it to the other one I have) mount and two cheap telescopes.
Yesterday afternoon I noticed the moon was up and decided to take a look. It was the first time that I used my reflector. The view would have been great if not for the spider and the secondary being visible ever so slightly, that ruined the whole experience. I added a barlow and the spider disappeared. I guess what I want to know is if anyone else had this issue and is there a different way to solve this. (Other than getting an expensive telescope) The telescope is Explore One, 114mm Aurora II, f/l 500mm. I did spend a few days learning how to collimate it prior to using it. I think I did everything correctly but could that be related? Or is it because the telescope is so fast? Or is it simply because it is so cheap?

What length eyepiece were you using when you were seeing the spider and secondary?  That would be caused by too low magnification.


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#4 JamesMStephens

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Posted 13 July 2020 - 07:41 PM

Yesterday afternoon I noticed the moon was up and decided to take a look. It was the first time that I used my reflector. The view would have been great if not for the spider and the secondary being visible ever so slightly, that ruined the whole experience. 

The spider and secondary support shouldn't be visible if you've focused the telescope on your target (the Moon in this case).


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#5 Nikolai

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Posted 13 July 2020 - 08:07 PM

Thank you for such a quick response!
The EP was 26 mm plossl that came with the telescope. I haven't tried any other ones. If the weather permits I'll try some other ones tonight. I did notice that focusing the object made the spider less visible but did not eliminate it completely.
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#6 JohnBear

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Posted 13 July 2020 - 08:22 PM

 

I did spend a few days learning how to collimate it prior to using it. I think I did everything correctly but could that be related?

Yes! - especially if you adjusted the secondary mirror.  That is sort of the biggest mistake newbies make with reflector telescopes. BTW that is not a bad Telescope for starting out, With about an hour of experienced instruction you will probably really enjoy using it a lot. Just about any local astronomer will be able to help you out, but it is much more difficult to do via forum posts.

 

Best advice for a beginner that wants to get into amateur astronomy is it join a local astronomy club, then look at and use what other astronomer have, to get some in-person advice and experience before buying a new telescope.  Did you know that many clubs offer classes and different types of telescope for people try out?

 

Of course Covid-19 complicates this, but many clubs now offer online meetings, etc.  Contact one, you might be surprised.  Also be sure  to get a good guide book for observing, "Turn Left at Orion" is considered on of the best for beginners.  There are also free planetarium apps that will be very useful when the scope is fully funcrional.

 

BTW - Welcome to CN, and keep us posted on how things are progressing.  


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#7 Goldengirl52

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Posted 13 July 2020 - 08:40 PM

You probably already have done this, but I'm a beginner too and thought I would ask you about the videos on Youtube.  I will be almost totally relying on them, and I do see at least 2 with info on how to set up and use your, particular Telescope.  I didn't spend a lot on mine either, but it's not arrived yet ;)  Maybe one of those vids would help you.  Here's the setup one in case you want to look.  There's another that I think has adjustments etc.

https://www.youtube....s&pbjreload=101



#8 vtornado

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Posted 13 July 2020 - 09:21 PM

Hello Nikolai, welcome to CN.

 

I agree with Chris,   you are viewing at too low a power.    That is why when you put the barlow in the secondary shadow disappeared.

Use the 10mm eyepiece, not the 26.  This is a common phenomenon in any telescope with a central obstruction when viewing the moon.

Also occurs if using your scope in the daytime too.  The 26 is fine to use when viewing dim objects, like star clusters.


Edited by vtornado, 13 July 2020 - 09:22 PM.

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#9 Jon Isaacs

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Posted 13 July 2020 - 09:22 PM

Yesterday afternoon I noticed the moon was up and decided to take a look. It was the first time that I used my reflector. The view would have been great if not for the spider and the secondary being visible ever so slightly, that ruined the whole experience. I added a barlow and the spider disappeared.

 

 

Nikolai:

 

What you saw was perfectly normal and had nothing to do with the collimation of your scope.

 

The focal ratio of your scope is F/4. That means the exit pupil, the beam of light that enters your eye is 

 

26 mm /4 = 6.5 mm.

 

You can actually see this by removing the cover your scope and looking at the eyepiece from a distance.

 

You will see a bright disk with dark hole in the center. That hole is the shadow of the secondary. Put you hand in front of the scope and you will see the shadow of your hand.

 

During the day, your eye is not dilated, your pupil is small, probably about the size of the shadow.  That's what you're seeing.

 

When you insert the Barlow, the 26 mm eyepiece becomes a 13 mm eyepiece, the exit pupil is now 13mm/4 = 3.25mm and the shadow will be much smaller. That's why it looked normal with the Barlow.

 

Try it and see. Insert the Barlow and you will see the exit pupil is 1/2 the size.

 

At night, when your eye is dilated to 6 mm or 7 mm this is not normally a problem.  

 

However it can be a problem viewing the moon since the moon is bright enough to cause your eye to contract.

 

I hope this all makes sense, what you saw was 100% normal.

 

Jon


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#10 gnowellsct

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Posted 13 July 2020 - 09:35 PM

Jon is correct in all the details.  It is "normal" for your f/4 scope.

 

The effect is not normal for all scopes.  In refractors it is not normal at all because you don't have a secondary to cast a shadow.  This is one of those +1 things that refractors have going for them.

 

In SCTs it is "seldom seen" because SCTs tend to be f/10 or f/11, so they operate at intrinsically higher magnification/smaller exit pupil.

 

During the daytime, however, you can get this effect with both Newts and SCTs.  Your daytime pupil (~1/2 mm) is so tiny that if a shadow is there it will succeed, at least sometimes, in blocking the light from getting into your eye.    Your 26 mm eyepiece in an f/10 SCT yields a 2.6 mm exit pupil (26/10).   That's substantially smaller than the 4 mm Jon writes about above, so it's more favorable to avoiding the shadow.  But during the day you can sometimes see these weird blackout effects.  

 

Your Barlow will reduce or eliminate the effect.  So will short focal length eyepieces in general.

 

Greg N


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#11 Chris Y

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Posted 13 July 2020 - 10:13 PM

Thank you for such a quick response!
The EP was 26 mm plossl that came with the telescope. I haven't tried any other ones. If the weather permits I'll try some other ones tonight. I did notice that focusing the object made the spider less visible but did not eliminate it completely.

26mm would be 19x.

 

I realize how frustrating it must have been, but I'm very happy you posted about it.  A little over a month ago I got the flat black Aurora II for my grandson as a target of opportunity due to the sale price.  I also bought him a refractor that dear old mom and dad have been enjoying for him since he's only 10 1/2 months old now.  I'll let them know about the possible shadow when using the 26mm eyepiece.

 

Cheers!

Chris



#12 physik

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Posted 13 July 2020 - 10:34 PM

Thank you for such a quick response!
The EP was 26 mm plossl that came with the telescope. I haven't tried any other ones. If the weather permits I'll try some other ones tonight. I did notice that focusing the object made the spider less visible but did not eliminate it completely.

Please be sure you give us a follow up on your experience with the scope once you find your way around it. I was looking online and the reviews are mixed for that scope, but the problems you're encountering are well covered by the others in the thread. It'll be cool to see if you're able to get some good use of out it. Good luck!


Edited by physik, 13 July 2020 - 10:34 PM.


#13 Nikolai

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Posted 13 July 2020 - 10:55 PM

Awesome! Thank you so much everyone for your advice. Everyone who thought it was the EP was absolutely correct! I tried a 20mm and there was absolutely nothing obstructing my view! Jupiter, Saturn and M22 ended up being my targets tonight. Like I said - Awesome! It was a great evening. Once again thank you all so much for your help! I will definitely continue with my new hobby. Local club is also a great idea. I will try that next.
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#14 Nikolai

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Posted 13 July 2020 - 11:03 PM

JohnBear I did pick up "Turn left at Orion" at the local library. It is a great book! It is actually thanks to that book I was able to find M22 tonight. Clear skies to all!
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#15 kfiscus

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Posted 13 July 2020 - 11:30 PM

I would encourage you to join us on CN often.  This is a GREAT family/club.


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#16 Nikolai

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Posted 13 July 2020 - 11:38 PM

Chris I do believe that Jon and Greg are right. It absolutely makes sense, size of the pupil and ability to accommodate all that light during the day. I haven't tried the 26mm tonight, but I would think the guys are correct and at night the EP won't give me any issues. Hopefully I'll get a chance to try that out soon.
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#17 Chris Y

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Posted 14 July 2020 - 01:46 AM

Chris I do believe that Jon and Greg are right. It absolutely makes sense, size of the pupil and ability to accommodate all that light during the day. I haven't tried the 26mm tonight, but I would think the guys are correct and at night the EP won't give me any issues. Hopefully I'll get a chance to try that out soon.

Your description was familiar to me.  I have a 0.5x reducer for my 152 Mak and, while I only experimented with it once, I recall it having a dark spot in the middle of the field of view when using a 35mm EP.  It took a minute, but then I realized it was the shadow of the secondary mirror, and it was due to too low magnification.  I need to play with that thing some more.  I looked back in my observing log and it was also vignetting with my 35mm 70° EP.


Edited by Chris Y, 14 July 2020 - 01:47 AM.


#18 Chris Y

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Posted 14 July 2020 - 02:09 AM

... Jupiter, Saturn and M22 ended up being my targets tonight. ...

I'm jelly!  By the time Jupiter and Saturn cleared the obstructions to the east of me I ended up with total cloud cover.



#19 phillip

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Posted 14 July 2020 - 03:44 AM

Alot to look forward to.

 

Planets are my favored, you'll be blown away with the Jupiter Saturn first view.

 

But best when sky behaves, are times images are boiling with poor sky, but keep looking and when sky settles loads of details pop into view. 

 

Happy Viewing!

 

Etx90

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Baader 30mm 

 

Clear Sky




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