First light with the Starfield 102 ED

[quasar117]

5 hours ago, Elp said:

Have you tried another refractor during the same night for comparison?

The only other equipment I now have is very s very cheap 60mm refractor from the 80's. Star test was so bad it showed two airy disks.  Yet no sign of flaring. But as another member pointed out, it could be due to exit pupil.

I also have a pair Zeiss Victory 10x42 bins that show pinpoint stars.

 

[quasar117]

5 hours ago, Mr Spock said:

Which diagonal are you using?

Brand new William Optics carbon dura bright 2" dielectric.

[dweller25]

I was also out last night looking at the Moon, seeing was very good until about 9pm after which it deteriorated.

However, your description suggests you are seeing spherical aberration which @Mr Spock did not see with his Starfield 102.

Manufacturing variances do occur, so It may be worth talking to your supplier.

[Nik271]

There is an easy way to test for spherical aberration using a 30% central obtruction mask (cut out a 30mm paper disc and attach it to the front of the dew shield with some thin strip of cellotape for example).

 

Aim at Polaris with a medium power EP, focus. Now defocus equal amounts of about 3mm either side and compare the doughnuts. Does the central hole look similar in the doughnut? If not - you have a spherical aberration.

 

Another way is with a Ronchi eyepice, which costs about £40 from FLO.

Edited April 18 by Nik271

[quasar117]

On 18/04/2024 at 08:24, Nik271 said:

There is an easy way to test for spherical aberration using a 30% central obtruction mask (cut out a 30mm paper disc and attach it to the front of the dew shield with some thin strip of cellotape for example).

 

Aim at Polaris with a medium power EP, focus. Now defocus equal amounts of about 3mm either side and compare the doughnuts. Does the central hole look similar in the doughnut? If not - you have a spherical aberration.

 

Another way is with a Ronchi eyepice, which costs about £40 from FLO.

Seeing for me wasn't bad tonight. Managed to compare views with and without a diagonal. Boths instances shared the same issue as before. So I'm confident it is not due to the diagonal.

Tomorrow I may try your obstruction mask idea to check for spherical aberration.

[Louis D]

On 17/04/2024 at 16:44, quasar117 said:

However, it was accompanied by flaring around the edge shooting off at symmetrical angles.

How long did you allow for acclimation?  I see spiking with my 90mm triplet APO that looks like pinched optics for up to about 30 minutes.  It eventually disappears after acclimation.  Give your scope an hour to acclimate and check again.

[mikeDnight]

Which eyepiece are you using? Is it one particular eyepiece or do different eyepieces show the same effect?Sometimes oily residue from eyelashes, oran accidental touch of the eye lens on the eyepiece can create a bluring effect on the image. Perhaps try cleaning the eyelens with a lens tissue or cloth.

[IB20]

What bright stars are you trying to see as pin point? Some of the brightest, simply wont appear like that. Also, have you managed to see airy disks and diffraction rings when you’ve cranked up the magnification?

[quasar117]

18 hours ago, Louis D said:

How long did you allow for acclimation?  I see spiking with my 90mm triplet APO that looks like pinched optics for up to about 30 minutes.  It eventually disappears after acclimation.  Give your scope an hour to acclimate and check again.

I gave it 45 mins to acclimatize with dust caps off.

[quasar117]

6 hours ago, mikeDnight said:

Which eyepiece are you using? Is it one particular eyepiece or do different eyepieces show the same effect?Sometimes oily residue from eyelashes, oran accidental touch of the eye lens on the eyepiece can create a bluring effect on the image. Perhaps try cleaning the eyelens with a lens tissue or cloth.

I can see it in all my EPs: 24mm ES 68°, 12.5mm Ortho, each focal length of the 3-8mm SVbony zoom. I mainly use the SVbony at 4mm to do the star test.

Can I use eyeglasses cleaner on the lens with a tissue/ cotton bud?

[quasar117]

5 hours ago, IB20 said:

What bright stars are you trying to see as pin point? Some of the brightest, simply wont appear like that. Also, have you managed to see airy disks and diffraction rings when you’ve cranked up the magnification?

Mainly, Polaris, Capella, Castor and Dubhe. The latter of which seems quite good to star test as it is quite close to zenith when I go out to observe.

The only time I don't see the diffraction ring is in extra-focus. Intra-focus shows the rings and in focus when the seeing has been good I can see the airy disk.

Also when I have observed Jupiter, albeit very low, it was showing this flaring affect aswell.

Borrowed my brother's spotting scope and couldn't see it evident when looking through that.

[IB20]

9 minutes ago, quasar117 said:

Mainly, Polaris, Capella, Castor and Dubhe. The latter of which seems quite good to star test as it is quite close to zenith when I go out to observe.

The only time I don't see the diffraction ring is in extra-focus. Intra-focus shows the rings and in focus when the seeing has been good I can see the airy disk.

Also when I have observed Jupiter, albeit very low, it was showing this flaring affect aswell.

Borrowed my brother's spotting scope and couldn't see it evident when looking through that.

Are you experiencing similar to this? https://www.cloudynights.com/topic/870714-interpreting-refractor-star-tests/

From reading what you’re seeing it doesn’t sound quite right and I wonder if you should contact your supplier to see if you could get it looked at or maybe even a replacement. 

[quasar117]

40 minutes ago, IB20 said:

Are you experiencing similar to this? https://www.cloudynights.com/topic/870714-interpreting-refractor-star-tests/

From reading what you’re seeing it doesn’t sound quite right and I wonder if you should contact your supplier to see if you could get it looked at or maybe even a replacement. 

Yes,  I'd say that is similar to what I am experiencing. Possible under correction.

I've contacted FLO and they have agreed to test it on their optical test bench. 

[mikeDnight]

10 hours ago, quasar117 said:

I can see it in all my EPs: 24mm ES 68°, 12.5mm Ortho, each focal length of the 3-8mm SVbony zoom. I mainly use the SVbony at 4mm to do the star test.

Can I use eyeglasses cleaner on the lens with a tissue/ cotton bud?

Yes, eyeglass cleaner is fine  and safe to use. Only spray it onto the tissue and nor directly onto the lens just in case it seeps between the elements. 

[apaulo]

Something quite simple, have you let another another astronomer look through the starfield. Or someone with decent to good eyesight. If they see what your seeing, get it back to the seller.  If not, get new eyeballs. lol. No need for rocket science.

[quasar117]

On 23/04/2024 at 08:23, apaulo said:

Something quite simple, have you let another another astronomer look through the starfield. Or someone with decent to good eyesight. If they see what your seeing, get it back to the seller.  If not, get new eyeballs. lol. No need for rocket science.

Had my wife look through it who admittedly is not and astronomer, but has good eyesight. She saw the same artifact as me on the stars and Jupiter.

The Starfield is currently away for testing at FLO. Will be interested to see what the outcome is.