fuzzy images

[mrmagoo]

Hi, Just joined today, Bought used Scope yesterday on Gumtree, Celestron astromaster 144. no instructions but managed to roughly set up on decking last night, When I used the 20mm finder piece to Moon was really clear and crisp image, when i removed and tried other lens supplied  10mm and a 6mm plossil all I could see was a really bright blur and could not focus , came with 6 fillters but not tried these yet and not sure what different filters would be used for, Any ideas, Thanks, Pat

[Davey-T]

Did you mean 114 ?

Dave

[D4N]

Hmm are you sure it is a 144?  I thought the largest Astromaster was 130 (this number is the diameter of the primary (large) mirror in mm).

 

It is generally best best to try out the scope in the day as it will be more obvious how to focus it, just be careful not to point it anywhere near the sun.

 

For the filters it depends somewhat on what they are, you can get neutral filters that are for making the moon dimmer, colour filters that are for making details on planets clearer, light pollution filters for filtering out the glow from street lights and nebulae filters for viewing the specific emissions from nebulae.

[mrmagoo]

27 minutes ago, mrmagoo said:

Hi, Just joined today, Bought used Scope yesterday on Gumtree, Celestron astromaster 144. no instructions but managed to roughly set up on decking last night, When I used the 20mm finder piece to Moon was really clear and crisp image, when i removed and tried other lens supplied  10mm and a 6mm plossil all I could see was a really bright blur and could not focus , came with 6 fillters but not tried these yet and not sure what different filters would be used for, Any ideas, Thanks, Pat

Sorry its 114 as you say. 

[Guest Tuomo]

You need to refocus everytime you switch eyepieces.

[JOC]

The filters might not be much use to you or they may be useful - it will depend on which ones they are.  Around the edge of each one should be some numbers, if you post up what the numbers are roughly what colour they are folks here might be able to help or try plugging the numbers you find into google.

[ronin]

According to Celestron the Astromaster 114 has a tube length of 457mm but a focal length of 1000mm, this means that it is a Bird-Jones type scope. Celestron have used a short focal length mirror then put a barlow type lens in the focuser to achieve a supposid 1000mm focal length. The whole problem is that Celestron didn't do it very well. In defence of Bird and Jones I suspect it is not a strict B-J implimentation but a less costly Synta way of doing it. Just do not want to do Bird or Jones (if different people) a disservice.

Owing to this the scope is best used for low and medium magnifications, I would simply suggest up to 80x which should show Jupiter fairly well, that would be a reasonable 12mm eyepiece. The supplied items will be Huygens type eyepieces and they are not great. You will likely want to try for 100x, 10mm eyepiece, and if so then get a semireasonable plossl. Try Alan at Sky's the Limit on ebay, think he has some at around the £24 area, sort of £24 +/- £2.

Reason for low to mediuum i that the barlow used will be an inexpensive item and adding a barlow again, 2 in a row, tends to not work.

If by chance you have a tube that is about 1000mm long and not just under 500mm then you have a "better" scope, that barlow in focuser really does nothing to help. Just according to Celestro it is 1000mm focal length and a tube of 457mm.

The other factor I read is that the scope also does terrestrial viewing and that again means another lump of glass to invert the image, this could also be degrading the image. Actually think it moves the image so this may account for not getting a focused image with the 10mm supplied item. The 10mm eyepiece may not be able to reach the image formed by the scope. Think I have encountered this previously with someone. Did thescope come with any short "extension" tubes that fit in the focuser, or are already in the focuser that can be removed ??

Have the idea this will be a case of what bits do you have, lets see where they can go and if that improves things. I have a Bresser that came with about 2 or 3 short extension tubes, just have to work out which is the appropriate one for using.

[mrmagoo]

On 5/8/2017 at 13:47, ronin said:

According to Celestron the Astromaster 114 has a tube length of 457mm but a focal length of 1000mm, this means that it is a Bird-Jones type scope. Celestron have used a short focal length mirror then put a barlow type lens in the focuser to achieve a supposid 1000mm focal length. The whole problem is that Celestron didn't do it very well. In defence of Bird and Jones I suspect it is not a strict B-J implimentation but a less costly Synta way of doing it. Just do not want to do Bird or Jones (if different people) a disservice.

Owing to this the scope is best used for low and medium magnifications, I would simply suggest up to 80x which should show Jupiter fairly well, that would be a reasonable 12mm eyepiece. The supplied items will be Huygens type eyepieces and they are not great. You will likely want to try for 100x, 10mm eyepiece, and if so then get a semireasonable plossl. Try Alan at Sky's the Limit on ebay, think he has some at around the £24 area, sort of £24 +/- £2.

Reason for low to mediuum i that the barlow used will be an inexpensive item and adding a barlow again, 2 in a row, tends to not work.

If by chance you have a tube that is about 1000mm long and not just under 500mm then you have a "better" scope, that barlow in focuser really does nothing to help. Just according to Celestro it is 1000mm focal length and a tube of 457mm.

The other factor I read is that the scope also does terrestrial viewing and that again means another lump of glass to invert the image, this could also be degrading the image. Actually think it moves the image so this may account for not getting a focused image with the 10mm supplied item. The 10mm eyepiece may not be able to reach the image formed by the scope. Think I have encountered this previously with someone. Did thescope come with any short "extension" tubes that fit in the focuser, or are already in the focuser that can be removed ??

Have the idea this will be a case of what bits do you have, lets see where they can go and if that improves things. I have a Bresser that came with about 2 or 3 short extension tubes, just have to work out which is the appropriate one for using.

Hi Ronin and thanks for the advise. There are no extension tubes and dont appear to have any in the focuser. It would appear to be the 457 tube 1000 focal length. Not had another chance to use as cloud and chores for the wife has kept be busy for last few nights. At the moment my ambition is to have a bit more understanding of how to use properly before the dark nights return. Thanks again. 

[mrmagoo]

On 5/7/2017 at 21:13, Tuomo said:

You need to refocus everytime you switch eyepieces.

Hi Tuomo, Trying to refocus but it never became clear, I will get my head round it and fuigre it all out but it will take more time, 

[mrmagoo]

On 5/8/2017 at 12:19, JOC said:

The filters might not be much use to you or they may be useful - it will depend on which ones they are.  Around the edge of each one should be some numbers, if you post up what the numbers are roughly what colour they are folks here might be able to help or try plugging the numbers you find into google.

Hi JOC, Managed to get the filter chart from Celestron web page and now have a better idea off what the various filters do. When i changed down to the 10mm from 20 finder I am wondering if thats when i should have use the filter as the 20mm image was good but the 10mm has way to bright and blurred, going to repeat what I did  but with filters in the eye piece on the 10mm and 6mm . Thanks again. Pat

[Guest Tuomo]

8 minutes ago, mrmagoo said:

Hi Tuomo, Trying to refocus but it never became clear, I will get my head round it and fuigre it all out but it will take more time, 

Heres the thing: During day point your scope at distant object. Any tree or light post will do. It just have to be -lets say- 100m away from you. Now insert your eyepiece and focus your image using focus knobs both sides of your focuser. Now you should be able to get crisp image. Now, change your eyepiece and do the same. 

Same principal goes with the stars. Only when there is night you might lose star when you are changing eyepiece and when your scope is not focused sometimes you see just black. When image is getting sharper you start to see light and all the sudden stars becomes crisp and sharp. 

ps. Forget those filters. At the moment you dont need those. 

[Cornelius Varley]

On ‎5‎/‎7‎/‎2017 at 20:35, mrmagoo said:

Hi, Just joined today, Bought used Scope yesterday on Gumtree, Celestron astromaster 144. no instructions but managed to roughly set up on decking last night, When I used the 20mm finder piece to Moon was really clear and crisp image, when i removed and tried other lens supplied  10mm and a 6mm plossil all I could see was a really bright blur and could not focus , came with 6 fillters but not tried these yet and not sure what different filters would be used for, Any ideas, Thanks, Pat

If the telescope was secondhand it might not be complete. Within the focuser of this type of telescope is a barlow type corrector lens which is part of the optical system. You can check to see if it there by taking a sheet of kitchen towel and rolling it into a tight tube. If the corrector is there you will feel resistance if you push the rolled kitchen towel down the focuser tube, if the corrector is missing then the towel will emerge out of the bottom of the focuser.

[mrmagoo]

40 minutes ago, Tuomo said:

Heres the thing: During day point your scope at distant object. Any tree or light post will do. It just have to be -lets say- 100m away from you. Now insert your eyepiece and focus your image using focus knobs both sides of your focuser. Now you should be able to get crisp image. Now, change your eyepiece and do the same. 

Same principal goes with the stars. Only when there is night you might lose star when you are changing eyepiece and when your scope is not focused sometimes you see just black. When image is getting sharper you start to see light and all the sudden stars becomes crisp and sharp. 

Set up scope in kitchen with doors open, focused on trees in the distance, changed lens and, Bingo, hey presto, The amount off adjustment between in focus and out of focus is minute so I assume with the moon or stars it must be a even less, Steady hand required . Now i have one probably really stupid question. Why is image upside down, Please be gentle with me ...

[Cornelius Varley]

7 minutes ago, mrmagoo said:

Set up scope in kitchen with doors open, focused on trees in the distance, changed lens and, Bingo, hey presto, The amount off adjustment between in focus and out of focus is minute so I assume with the moon or stars it must be a even less, Steady hand required . Now i have one probably really stupid question. Why is image upside down, Please be gentle with me ...

The amount of adjustment between in and out of focus can be small and if you wind the focuser in/out too quickly you can miss the point of focus quite quickly. It is normal for the image to be upside down in a reflector and you won't notice this so much when looking at the stars because you won't have a point of reference as to what is up or down in the eyepiece. You will so become accustomed to the inverted image.

[mrmagoo]

25 minutes ago, Cornelius Varley said:

If the telescope was secondhand it might not be complete. Within the focuser of this type of telescope is a barlow type corrector lens which is part of the optical system. You can check to see if it there by taking a sheet of kitchen towel and rolling it into a tight tube. If the corrector is there you will feel resistance if you push the rolled kitchen towel down the focuser tube, if the corrector is missing then the towel will emerge out of the bottom of the focuser.

Hi, If i could see the Moon crisp and clear with the 20mm finder and not the 10mm or 6mm  I assumed the corrector must be there?

[Cornelius Varley]

1 hour ago, mrmagoo said:

Hi, If i could see the Moon crisp and clear with the 20mm finder and not the 10mm or 6mm  I assumed the corrector must be there?

If you get a sharp image with the 20mm then the corrector should be there. You just need to wind the focuser in/out slowly to find the sharpest view with the higher mag eyepieces. My technique is to wind the focuser inwards until you find focus then wind the focuser inwards a little more beyond the sharpest image then slowly wind the focuser out again until you are back in focus.

[mrmagoo]

12 minutes ago, Cornelius Varley said:

If you get a sharp image with the 20mm then the corrector should be there. You just need to wind the focuser in/out slowly to find the sharpest view with the higher mag eyepieces. My technique is to wind the focuser inwards until you find focus then wind the focuser inwards a little more beyond the sharpest image then slowly wind the focuser out again until you are back in focus.

Just came back indoors, Really clear night and great images of the moon with 20mm finder and 10mm. Tried the 6mm but nothing. Possibly due to Scope being basic  model and pushing beyond its capability But very pleased with what I have seen so far. Thank you very much, Pat.

[JOC]

As to the why is the image upside down that's to do with the way the curves and mirrors reflect the light rays around the various surfaces in a reflector.  If you Google a schematic of how a reflecting telescope works you will be able to how the light rays invert as they reflect off mirrors and pass through lenses and refract.  The net effect in a reflector is an upside down image.  As already noted above you won't notice it on sky based objects, but initially you need to remember that things are back to front and upside down if trying to find things from pictorial star maps.  FWIW I think it is the case that our eyes actually see an upside down image that our brain instantly corrects.  I've always found that difficult to believe, but I don't think it's an 'old wives tale'.