Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Starting again with 102ED f/7. Problem detected?

  • Please log in to reply
21 replies to this topic

#1 Astroview

Astroview

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 16 Sep 2020

Posted 16 September 2020 - 08:17 AM

Hi all,

 

I've been away from astronomy for a while but a few days ago I decided to have a look at Saturn and Jupiter with my Astro Professional 102mm f/7 (on a AZ4 with steel tripod).

When I set the telescope outside, I decided to have a daytime look. I switched through my eyepieces one by one. These are:

 

-Paragon 35mm (TS-Optics Paragon ED 2")
-Baader Hyperion 17mm
-Baader Hyperion 8mm
-Baader Hyperion 5mm

 

Now, it has been several years since I last used it. The 35mm was very sharp, couldn't be much better to my eyes.
The 17mm was still very sharp. No issues there, apart from slight CA around bright objects.
But starting with the higher magnifications, I noticed degradation of the image. The 8mm was still very usable, but already you could see more CA and a loss of sharpness.
The 5mm was definitely not wat I expected. It obviously enlarged the object in view but apart from that, it was difficult to get a sharp focus and CA was very much there. I didn't get much improvement from going from 8mm to 5mm because of this.

 

Viewing Jupiter and Saturn later in the evening confirmed the above.

My question is now: can I contribute this to my eyepieces, or should I look at my telescope for a possible problem?

 

I'm interested again in astronomy and in the last few weeks I've been reading and contemplating if I should buy a refractor system that is lighter, and which I can use on a lighter mount, and possibly a few
better eyepieces like Morpheus (for example), to stay in the Baader family.

I was thinking about a good FPL53 72mm tot 80mm refractor on a photo tripod. But maybe this question is best in a thread of its own.
Before I'd do this, I would like to know were I can locate the problem above.



#2 Echolight

Echolight

    Viking 1

  • -----
  • Posts: 908
  • Joined: 01 May 2020
  • Loc: Texas

Posted 16 September 2020 - 08:47 AM

I'm surprised by the CA as these are supposed to be the same Kunming United scope that is mostly highly regarded. Although I'm not well informed concerning those eyepieces.

 

But not surprised that 143x wasn't full of detail in a 4 inch f7 scope without knowing the specifics of the seeing/atmospheric conditions.



#3 Couder

Couder

    Ranger 4

  • *****
  • Posts: 390
  • Joined: 24 Feb 2014
  • Loc: Missouri Ozarks

Posted 16 September 2020 - 08:55 AM

Seeing, or sky clarity, could be the problem. Especially now with the fires in CA.



#4 sg6

sg6

    Cosmos

  • *****
  • Posts: 8,767
  • Joined: 14 Feb 2010
  • Loc: Norfolk, UK.

Posted 16 September 2020 - 09:34 AM

Where are you located ?



#5 Astroview

Astroview

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 16 Sep 2020

Posted 16 September 2020 - 10:58 AM

I'm located in Belgium. I'm surprised by the CA as well, that is, at higher magnifications.

For the test a chimney at approx 60-70 meter was used. There was a cooperative pigeon on there. With my 17mm, I could literally count mosquitos flying there!

So to my surprise, at 8mm it got cleary worse but still doable. And at 5mm, it was difficult to get a point in focus and the overall sharpness was, well , not good.. But the results where basically the same when viewing planets.

 

It's my only scope, so I have no way to compare with other equipment.



#6 SeattleScott

SeattleScott

    Cosmos

  • *****
  • Posts: 8,781
  • Joined: 14 Oct 2011

Posted 16 September 2020 - 11:59 AM

Just to be clear, is your 4” F7 an Apo or achro?

#7 coopman

coopman

    Fly Me to the Moon

  • *****
  • Posts: 6,527
  • Joined: 23 Apr 2006
  • Loc: South Louisiana

Posted 16 September 2020 - 12:07 PM

Says ED in the title, so it's probably a lot better than a crown & flint achro.  



#8 coopman

coopman

    Fly Me to the Moon

  • *****
  • Posts: 6,527
  • Joined: 23 Apr 2006
  • Loc: South Louisiana

Posted 16 September 2020 - 12:08 PM

Is your objective lens clean?



#9 tony_spina

tony_spina

    Mercury-Atlas

  • *****
  • Posts: 2,936
  • Joined: 14 Jun 2004
  • Loc: So. Cal.

Posted 16 September 2020 - 12:30 PM

Do you have access to other eyepieces you can try?  Have you also tried to view without the diagonal?.... trying to rule these items out as the issue 



#10 SeattleScott

SeattleScott

    Cosmos

  • *****
  • Posts: 8,781
  • Joined: 14 Oct 2011

Posted 16 September 2020 - 12:42 PM

Ok even assuming FPL51 equivalents it shouldn’t have intrusive CA at 100-150x.

That leaves the eyepieces or seeing, atmosphere dispersion, etc.

Let’s start with the eyepieces. I haven’t tried any Hyperion due to the very lukewarm reviews but I get the impression the 21 and 17 are the best and the 13 might be the worst. Recently I read a thread about the 8 being subpar and I might have read very recently about the 5 being particularly poor but I cannot recall for sure. So the eyepieces could certainly be contributing. But in general most people say Hyperion is fine at F6 and up so they shouldn’t be destroying the view.

So let’s look at atmospheric dispersion. The planets Jupiter and Saturn are not all that high in the sky, and could be rather low depending on when you view them. A blue/violet halo around Jupiter is CA, but blue at the bottom and red at the top (or vice versa) is atmospheric dispersion. FPL53 can fix CA. Moving near the equator can fix atmospheric dispersion. Waiting for planets to get higher in the sky or using a ZWO ADC can help with atmospheric dispersion to an extent, and might be more practical than moving to the equator.

Seeing is another potential culprit. If it looks like waves of water are flowing over the planets, that would indicate seeing issues or cooldown. It is summer where you are so cooldown probably isn’t a major issue. Most nights 100-150x should be fine though, and you talked about seeing color error, so I have a feeling that seeing isn’t the culprit.

So what’s next? Try viewing targets higher in the sky. If the issue really is CA, then you will see obvious blue halo around bright stars high in the sky. This would indicate there is likely something wrong with your lens, or those eyepieces are really bad. The Double Double in Vega is a good test for optics. Should be able to barely split it at 143x.

Scott
  • db2005 likes this

#11 T1R2

T1R2

    Mercury-Atlas

  • -----
  • Posts: 2,922
  • Joined: 11 Jun 2013
  • Loc: NeverWhere, 35*N

Posted 16 September 2020 - 12:47 PM

When views are sharp at low power but get worse at high power,after the other suggestions.... I look at collimation.



#12 db2005

db2005

    Apollo

  • *****
  • Posts: 1,223
  • Joined: 23 Dec 2017
  • Loc: Living in Denmark, under Bortle 5/6 skies.

Posted 16 September 2020 - 12:47 PM

Daytime viewing is frequently heavily affected by thermal currents rising from the ground due to the heat of sunlight. There's good reason we very rarely see spotting scopes with more than ~90 mm aperture.

 

If I were in your shoes I would try again at night, make sure the scope is properly acclimatized, and see if the problem persists. If it does, try a star-test with your 5 or 8 mm eyepiece, and look for any problems. Lack of sharpness can be caused by spherical aberration (SA) which is easily detectable with a star test. Also, try viewing without the diagonal in place - if the diagonal mirror has been knocked out of alignment, that too can degrade the image considerably.

 

Btw. I used to own a couple of Hyperions. They both showed noticeable amounts CA and lateral color, so I wouldn't immediately blame CA on the scope itself. CA is frequently easier to see in daylight than at night, e.g. tree branches against a bright blue sky, so I wouldn't panic just yet.



#13 SeattleScott

SeattleScott

    Cosmos

  • *****
  • Posts: 8,781
  • Joined: 14 Oct 2011

Posted 16 September 2020 - 12:57 PM

BTW I have six scopes, Apo, achro, Mak, Newts, a little of everything. I have mostly expensive Japanese eyepieces. Whenever I look at a particularly bright star, I see a wide white halo around it. With all of my scopes and all of my eyepieces. The views are still very sharp . This is not CA.

But you are talking about views getting soft too, at lower powers than they should typically start getting soft. So something is going on. Could be you are viewing the planets too low in the sky. Could be the eyepieces. Could be the refractor. Viewing targets high in the sky can rule out one of those.

Scott

#14 Eddgie

Eddgie

    ISS

  • *****
  • Posts: 26,936
  • Joined: 01 Feb 2006

Posted 16 September 2020 - 12:58 PM

I had a 110mm f/7 with FPL-51 ED glass and it was far from being color free.  In particular, on the sun, there was considerable contrast lost (vs a 4" Apo),

Even my 80mm f/7 ED scope showed considerable color error on the sun, which admittedly is a worst case test, but this just makes it easy to see the error. The error is always there. I would not expect much difference at 100mm.

 

At 4" and f/7, I think one needs to really go to FPL-53 but even then, I would not expect Apo performance. The 100ED at f/9 with FPL53 is Apo but f/7 is kinda fast for a doublet with FK61.  A triplet using FK61 would likely be much closer to an Apo.

 

Now an ED scope is in most cases going to be far better than an equal aperture and speed Achromat, but they are not Apos. 

 

I am not saying nothing is wrong with your scope... Maybe something is.  What I am saying is that it is not an Apo design and seeing color error is consistent with the aperture, focal ratio, and the glass used. 



#15 Astroview

Astroview

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 16 Sep 2020

Posted 16 September 2020 - 01:02 PM

Guys,

 

it's all solved. It turns out that the diagonal wasn't inserted all the way into the telescope, by almost half a cm. I'm slightly ashamed to admit that and I'm sorry to have bothered everyone, but am thankful for all your help.

 

One for the bloopers of the year.
 


  • MortonH, eros312, gnowellsct and 5 others like this

#16 SeattleScott

SeattleScott

    Cosmos

  • *****
  • Posts: 8,781
  • Joined: 14 Oct 2011

Posted 16 September 2020 - 01:05 PM

Guys,

it's all solved. It turns out that the diagonal wasn't inserted all the way into the telescope, by almost half a cm. I'm slightly ashamed to admit that and I'm sorry to have bothered everyone, but am thankful for all your help.

One for the bloopers of the year.

Interesting, that shouldn’t impact the view though unless it was in slightly crooked.
  • coopman and Astroview like this

#17 db2005

db2005

    Apollo

  • *****
  • Posts: 1,223
  • Joined: 23 Dec 2017
  • Loc: Living in Denmark, under Bortle 5/6 skies.

Posted 16 September 2020 - 01:35 PM

Guys,

 

it's all solved. It turns out that the diagonal wasn't inserted all the way into the telescope, by almost half a cm. I'm slightly ashamed to admit that and I'm sorry to have bothered everyone, but am thankful for all your help.

 

One for the bloopers of the year.
 

Don't worry. You are not the first person to make that mistake - and certainly not the last :). Glad it worked out for you in the end.


  • Astroview likes this

#18 RichA

RichA

    Vanguard

  • *****
  • Posts: 2,204
  • Joined: 03 Jun 2010
  • Loc: Toronto, Canada

Posted 16 September 2020 - 11:30 PM

Seeing, or sky clarity, could be the problem. Especially now with the fires in CA.

I'm Toronto and the only thing visible was Mars the other night.  This reminds me of the late 1980's when a big volcano blew up somewhere out East and filled the stratosphere with crap.  At the time,  I thought there was something wrong with the SCT I had, but it turned out to be the particulate matter in the atmosphere.  It finally went away, the scope was fine.


Edited by RichA, 16 September 2020 - 11:31 PM.


#19 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 17,847
  • Joined: 24 Jun 2009

Posted 17 September 2020 - 04:40 PM

Seeing, or sky clarity, could be the problem. Especially now with the fires in CA.

I don't think so.  Not for the CA with magnification on daytime landscape.

 

The actual daytime test for CA is a distant branch at high magnification against a bright blue sky.    When my CFF arrived (triple) I took it up to 720x which is almost 8x per mm (2x per mm is considered maximum reasonable) and detected no color.  But that was with a 3.5XW sitting on top of a 4x Powermate.

 

A good ED scope should be able to handle a 5mm ocular without going all color-y.  

 

But I am unfamiliar with this brand and it doesn't come up on google.  Is it the same as Astronomics AT102 f/7?

 

Greg N



#20 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 17,847
  • Joined: 24 Jun 2009

Posted 17 September 2020 - 04:41 PM

Guys,

 

it's all solved. It turns out that the diagonal wasn't inserted all the way into the telescope, by almost half a cm. I'm slightly ashamed to admit that and I'm sorry to have bothered everyone, but am thankful for all your help.

 

One for the bloopers of the year.
 

whoops.  OK.  You might do the daytime branch test anyhow.  The scope should pass the test.  It may not pass the test inside and outside of focus, but in focus, it should pass the test.

 

Greg N



#21 helpwanted

helpwanted

    Fly Me to the Moon

  • *****
  • Posts: 5,080
  • Joined: 04 Jul 2007
  • Loc: Phoenix, AZ

Posted 17 September 2020 - 04:43 PM

I say this respectfully, but as we get older, our eyes can be a problem as well (mine are 55 yrs old), so before blaming your scope or eyepieces, how is your vision? Been to an eye doctor lately? 


  • BFaucett likes this

#22 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 17,847
  • Joined: 24 Jun 2009

Posted 17 September 2020 - 04:44 PM

Guys,

 

it's all solved. It turns out that the diagonal wasn't inserted all the way into the telescope, by almost half a cm. I'm slightly ashamed to admit that and I'm sorry to have bothered everyone, but am thankful for all your help.

 

One for the bloopers of the year.
 

Actually the blooper of the decade was when I got a Televue Dioptrx and had it on an eyepiece and forgot it was there. 

 

Next time I set up my something was wrong even though the collimation was good.  Only after I had wasted an hour rotating the corrector plate did I realize that the astigmatism was coming from the Dioptrx which has to be at exactly the right position to correct astigmatism rather than induce it.

 

Greg N




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics