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Upgrade achromat 152 mm F5.9 for DSO AP.

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#1 aristo

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Posted 11 September 2019 - 01:24 PM

I would like to have your advice about upgrading Achromat refractor 152mm F5.9 (which I own) , for DSO AP.
Any additional upgrades for this 152 achromat, within budget .
I know and experienced , the blue chromatic aberration issue when visual high intensity objects like moon and planets.
(The scope is TS-Optics 6" f/5.9 Refractor - 2.5" R&P Focuser - Ohara (Japan) Objective)
Could be (within budget)any upgrades to improve its DSO photography abilities.
I have V block filter , UHC filter, ZWO 1.25inch FILTER WHEEL + ZWO 1.25 inch  LRGB filters, but didn’t used them yet, with the achromat.
I'm trying several setups (that I own)  for  DSO photography as part of my AP beginner practicing and learning. 
I'm practising with 2 setups :
Meade SCT 8inch ACF + f6.3 reducer + NIKON D90+ Losmandy G11 EQ mount Guided
Achromat refractor 152 mm F5.9 +NIKON D90+ Losmandy G11 EQ mount. Guided.
  I'm practicing different kinds of setups just for learning and getting experienced  before purchasing dedicated  camera  ( ZWO ASI 1600 mono, or  071color ,or 294 color)
Don’t want to jump over my budget  (Till now bought 10 different kinds of scopes and mount for visual , including dobsonian , achromats, EQ mounts and AZ mounts ,  My wife will stop my endless astro shopping)
Twice a month I drive (200 km)  to 3 bortle area.
Not far from my home (20 km) There is  4.5  bortle area.



#2 John Tucker

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Posted 11 September 2019 - 01:41 PM

There are a bunch of chromatic aberration filters discussed here.  https://www.cloudyni...r-to-reduce-ca/


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#3 zxx

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Posted 11 September 2019 - 02:43 PM

I did a little AP with my 127mm F 9.4 achromat, If you stay away from bright stars the better the results.

Here is one I did of M51. The longer the FL the more forgiving they are with the blue halos around stars.

 

12 m51 22.jpg


Edited by zxx, 11 September 2019 - 02:47 PM.

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#4 aristo

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Posted 11 September 2019 - 04:06 PM

There are a bunch of chromatic aberration filters discussed here.  https://www.cloudyni...er-to-reduce-ca

 

I did a little AP with my 127mm F 9.4 achromat, If you stay away from bright stars the better the results.

Here is one I did of M51. The longer the FL the more forgiving they are with the blue halos around stars.

 

attachicon.gif 12 m51 22.jpg

Wow

very beautiful image. Very encouraging that you have gotten it with achromat. Have you used any special filters . Which camera used for this beautiful image.


Edited by aristo, 11 September 2019 - 04:12 PM.


#5 zxx

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Posted 11 September 2019 - 04:15 PM

 John,

 

Wow

very beautiful image. Very encouraging that you have gotten it with achromat. Have you used any special filters . Which camera used for this beautiful image.

Thanks ,no filters. The stars in the image are mag 9 or less so not to bad. Pentax K50.



#6 aristo

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Posted 11 September 2019 - 04:16 PM

There are a bunch of chromatic aberration filters discussed here.  https://www.cloudyni...r-to-reduce-ca/

John

Thanks for the link.

Just now I'm reading it , Hopfully to find the right advice from the experienced guys.



#7 John Tucker

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Posted 11 September 2019 - 04:38 PM

Somebody on this site, I don't remember their name, posts some real nice pics using an achromat and the Baader filter. Don't remember what OTA or focal length.

#8 aristo

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Posted 11 September 2019 - 05:07 PM

Somebody on this site, I don't remember their name, posts some real nice pics using an achromat and the Baader filter. Don't remember what OTA or focal length.

This is just what I'm looking for . Results of using Achromat + recommended filter . Same as ZXX posted above .

My achromat is F5.9 so it will abberate the blue stronger than ZXX telescope which is F9.4 . But he didnt use any filter just recommended to keep away from bright stars.


Edited by aristo, 11 September 2019 - 05:10 PM.


#9 Im2bent

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Posted 11 September 2019 - 05:16 PM

You might want to read this before you buy the 294 or 1600

https://www.cloudyni...t-triad-and-nb/



#10 aristo

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Posted 11 September 2019 - 05:17 PM

My dealer which is aphotographer by himself suggested using ZWO narrow band filters + 1600 mm camera , saying it will absolutly solve the CA problem.

But till I come to the right decision about which setup to go with , I would prefer continue experiments with the 2 setups +NIKON D90 , I've mentioned above.



#11 John Tucker

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Posted 11 September 2019 - 05:30 PM

You can go narrowband but I suspect its overkill. I think the main issue is the shorter wavelengths, and that the filters designed to take those out will prob do the job.

#12 zxx

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Posted 11 September 2019 - 06:02 PM

Here is a post I started two years ago, I also posted a pic of M81 M82 you can see the halos around the brighter stars.

 

https://www.cloudyni...-f94-refractor/



#13 aristo

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Posted 11 September 2019 - 06:37 PM

You might want to read this before you buy the 294 or 1600

https://www.cloudyni...t-triad-and-nb/

Thanks , the more I read about 294 issues, the less my interest in 294 decreases.  So 2 option left 071 or 1600 + NB filters. So my interest is restricted to one of two : ZWO ASI 071 , or 1600+ NB, with greater preference towards 071, as it also allowed to be used as one shoot camera,(life is easier with one shoot ) as well as using it with NB filters under air polluted sky, or when used with achromat refractor as mine F5.9 .



#14 aristo

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Posted 11 September 2019 - 06:47 PM

post-103547-0-47538600-1487769180_thumb.jpg

Here is a post I started two years ago, I also posted a pic of M81 M82 you can see the halos around the brighter stars.

 

https://www.cloudyni...-f94-refractor/

ZXX

Its amazing what excellent DSO image you've got with this simple setup of yours , I will attach your setup from your post, again here

It proves that not only the equipment but the photographer...  as about the blue halos around m81 it appear since you have not used filters , might be improved with the right filter .. This is what I'm looking for filters for achromat , next session ( end of September)  I'll try the V block filter which I own , I'll post the images . But still looking for better filters .


Edited by aristo, 11 September 2019 - 07:40 PM.

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#15 John Tucker

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Posted 12 September 2019 - 12:33 PM

Do us a favor and post some results when you've picked something out. 



#16 aristo

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Posted 12 September 2019 - 07:58 PM

Do us a favor and post some results when you've picked something out. 

John .
I will do it for sure.
I'm waiting for the new moon at the end of September ,
Going to use the achromat 152 F5.9 + V block filter. under dark sky
3 bortle
Mount Losmandy G11 Guided.
I'm greatly hoping to get successful results with this setup.
I think it will be an interesting experiment.


Edited by aristo, 12 September 2019 - 07:59 PM.

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#17 zxx

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Posted 12 September 2019 - 10:45 PM

John .
I will do it for sure.
I'm waiting for the new moon at the end of September ,
Going to use the achromat 152 F5.9 + V block filter. under dark sky
3 bortle
Mount Losmandy G11 Guided.
I'm greatly hoping to get successful results with this setup.
I think it will be an interesting experiment.

Now that I have a little more experience with the hobby and a better mount to carry my 127mm f9.4 I may also try it again.


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#18 drd715

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Posted 14 September 2019 - 10:56 PM

My dealer which is aphotographer by himself suggested using ZWO narrow band filters + 1600 mm camera , saying it will absolutly solve the CA problem.

But till I come to the right decision about which setup to go with , I would prefer continue experiments with the 2 setups +NIKON D90 , I've mentioned above.

The  way this "narrow band" mono camera type of astrophotography is able to defeat CA is that the color frequencies when taken with a one shot color camera don't come to focus at the same length so you can only focus one fairly narrow part of the spectrum while the other color frequencies are slightly out of focus. If you filter to a narrow frequency around each primary color (plus some specialty frequencies such as Ha)  you will focus each color separately so all is in focus. Shooting each channel in mono you then process them separately,  assign them their proper color in a software program and add them back together (basically) .  This is a challenging task  But it actually produces the best image  It takes about 5 times the imaging and five times the processing as compared  to a one shot  color process. The down side of osc is that you really need an APO telescope if under about F-7 or an ED scope is not too bad above F-7.  While an Achromat will  work ok above about F-10, F-12 to F-15 will show little CA.  Long FL disadvantage is slower collection of light requiring longer exposures and the associated problems of long exposure tracking plus messed up subs from satellite or aircraft passes through the exposure.  FL in mm is really a function of the size object you are trying to image. Small objects can be challenging especially in the beginning. The tracking has to be really tight.  So overall in the beginning it will be easier (less discouraging ) to start with an APO in the 100mm F-7 or less (triplet because of the shorter "F" number).  Also they are small enough not to over load the stability of the mount  which should be rated at two times the maximum load of all the  gear it is carrying,  ota,  Camera  guide scope, finder etc.  Problem is this stuff is not cheap. It can be had preowned for a big savings.  Just have a look in the CN classifieds.  

 

You may find the use of a filter to remove  some of the CA problematic in regards to the un-natural color shifting as the filters take out some of the color spectrum in the process of reducing the CA. 

 

Go ahead and experiment with what you have and if you are having fun then you can move up the ladder a bit better as time,  money, desire and your wife allow. 


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#19 aristo

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Posted 15 September 2019 - 01:01 PM

The  way this "narrow band" mono camera type of astrophotography is able to defeat CA is that the color frequencies when taken with a one shot color camera don't come to focus at the same length so you can only focus one fairly narrow part of the spectrum while the other color frequencies are slightly out of focus. If you filter to a narrow frequency around each primary color (plus some specialty frequencies such as Ha)  you will focus each color separately so all is in focus. Shooting each channel in mono you then process them separately,  assign them their proper color in a software program and add them back together (basically) .  This is a challenging task  But it actually produces the best image  It takes about 5 times the imaging and five times the processing as compared  to a one shot  color process. The down side of osc is that you really need an APO telescope if under about F-7 or an ED scope is not too bad above F-7.  While an Achromat will  work ok above about F-10, F-12 to F-15 will show little CA.  Long FL disadvantage is slower collection of light requiring longer exposures and the associated problems of long exposure tracking plus messed up subs from satellite or aircraft passes through the exposure.  FL in mm is really a function of the size object you are trying to image. Small objects can be challenging especially in the beginning. The tracking has to be really tight.  So overall in the beginning it will be easier (less discouraging ) to start with an APO in the 100mm F-7 or less (triplet because of the shorter "F" number).  Also they are small enough not to over load the stability of the mount  which should be rated at two times the maximum load of all the  gear it is carrying,  ota,  Camera  guide scope, finder etc.  Problem is this stuff is not cheap. It can be had preowned for a big savings.  Just have a look in the CN classifieds.  

 

You may find the use of a filter to remove  some of the CA problematic in regards to the un-natural color shifting as the filters take out some of the color spectrum in the process of reducing the CA. 

 

Go ahead and experiment with what you have and if you are having fun then you can move up the ladder a bit better as time,  money, desire and your wife allow. 

Thank you very much for detailed explanation.
After much astronomy shopping been done for visual , I have learned that there is no such unic telescope for all kinds of DSO.
Now I'm more carefull. I'll come to decision after tests and consultations.
You know how you start astronomy shopping , but don't know at first that astronomy shopping is endless untill your wife stop you.
Any way, AP is very much different then Visual .
In AP the mount is much more important then the Tube.
Fortunately I have a good one,  Losmandy G11 GEMINI 2 load capacity is 60 LB . I do have different kind of tubes and the help of the excellent guys in Claudy Nights that are willingly to consult and help.
I do enjoy those star parties under the dark sky ,with friends and the ability to try different kinds of setups.
As I have promised ,I will load the results here with Achromat + V block filter + G11 mount.+ Guiding
As you mentioned I might finish with APO telescope . Budget will limit  posibilities.


Edited by aristo, 15 September 2019 - 01:16 PM.



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