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Explore scientific refractors

Posted: Sun Feb 16, 2020 1:25 pm
by Tomcat
I have a celestron 8se now and planet images are ok not very crisp. Looking for a refractor for visual use only to mount on my meade lx85 mount. Anyone use the ar102, ar127,ar157 or the ed102. Which one would do better for medium to high power planet and dso viewing. Thanks

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 3:32 pm
by AbbN
I have the AR102 F/6.3 and love it but use it strictly for wide field viewing as it's best suited for that. As far as using it for planets it's ok although I never use it for that. My Celestron Omni XLT 120 F/8.3 is far better suited for planets and doubles than my AR102. Not sure about how well the AR127 is on planets but I'm sure someone else here will chime in regarding it. The AR152 is a beast and once considered it but backed down because of it's size.

Hope this helps
Abb

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 5:49 pm
by helicon
I have the AR 152 at f/6.5 - it works well for the moon and planets as I have noticed but really excels at deep sky views at low power of clusters and galaxies. For the planets, I take the magnification up to 220x or so. It's a pretty large/bulky scope to handle - need to carry the mount outside and then the OTA, which is slung into the dovetail mount. I have a Twilight II tripod.

Image

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 5:58 pm
by Refractordude
For planets and the moon I would go with the ED102. It is a f/9 with ED glass, so no violet color at high powers. I like the AR152 also, but with a 90mm aperture mask to cut down on the violet color. However, I read that some AR152s have very little to no violet color at around 200 magnification.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 6:01 pm
by Bigzmey
Tomcat, did you check collimation of your 8se? I had many refractors over the years from 80mm to 150mm, and none of them was better on planets than my 8" SCT.

If you want sharper views you should consider slow F10-13, or APO/ED refractors.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 6:49 pm
by Refractordude
Tomcat:

Maybe more cool down time. Check this out. http://www.astronomyforum.net/catadiopt ... n-sct.html

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 8:05 pm
by Don Quixote
For visual the AR152 does very well on the lunar views for me. On DSO it is an absolutely wonderful tool. On the bright, concentrated Jupiter, and Saturn views it does show color. Mars is good. Venus is loaded with color. But keep in mind the EP you use can mitigate the color fringe issue. For imaging the planets I prefer my ES127 FCD100 APO. You will need to pick what you want most to view.
High power on the planets is highly dependent on your atmospheric conditions as you well know. When the atmosphere is less than great my 100MM f9 Skywatcher is the tool I go with.
I have an older Meade LXD75 8" SCT that performs very well on the planets.
If I were going to add to my kit and I had only an 8" SCT in my stable I would go with the 102ED.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 8:23 pm
by stewe
Not an exact answer to your question, but I would like to second Bigzmey. If your C8 is properly collimated, cooled down, and you have good seeing, then according to the laws of optics, it should not give worse views on planets than any of the refractors you mentioned, unless it is defective.
So I suggest to collimate your scope or get it collimated, it will be cheaper than buying a new scope.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 8:37 pm
by notFritzArgelander
Bigzmey wrote: Sun Feb 16, 2020 6:01 pm Tomcat, did you check collimation of your 8se? I had many refractors over the years from 80mm to 150mm, and none of them was better on planets than my 8" SCT.

If you want sharper views you should consider slow F10-13, or APO/ED refractors.
Bigzmey wrote: Sun Feb 16, 2020 6:01 pm Tomcat, did you check collimation of your 8se? I had many refractors over the years from 80mm to 150mm, and none of them was better on planets than my 8" SCT.

If you want sharper views you should consider slow F10-13, or APO/ED refractors.
I agree. There is almost no way an achromatic refractor less than 130mm is going to do as well on planetary contrast as an 8" SCT all other things being equal.

The things that need to be equal are: collimation needs to be right, atmospheric seeing conditions need to support the higher resolution from the 8", the 8" needs to be thermally stabilized.

There is one other factor that would need to be considered once all the above has been taken into account: the eye behind the eyepiece.

I find that on lunar and planetary that SCTs seem soft to me. However an aplanatic SCT like the Celestron Edge series does superbly well. Some individuals are much more sensitive to curvature of the field of view. I'm one of them. You might be too. Before making a purchase eliminate collimation and cool down as problems, etc.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 8:39 pm
by Refractordude
notFritzArgelander wrote: Sun Feb 16, 2020 8:37 pm
Bigzmey wrote: Sun Feb 16, 2020 6:01 pm Tomcat, did you check collimation of your 8se? I had many refractors over the years from 80mm to 150mm, and none of them was better on planets than my 8" SCT.

If you want sharper views you should consider slow F10-13, or APO/ED refractors.
Bigzmey wrote: Sun Feb 16, 2020 6:01 pm Tomcat, did you check collimation of your 8se? I had many refractors over the years from 80mm to 150mm, and none of them was better on planets than my 8" SCT.

If you want sharper views you should consider slow F10-13, or APO/ED refractors.
I agree. There is almost no way an achromatic refractor less that 150mm is going to do as well on planetary contrast as an 8" SCT all other things being equal.

The things that need to be equal are: collimation needs to be right, atmospheric seeing conditions need to support the higher resolution from the 8", the 8" needs to be thermally stabilized.

There is one other factor that would need to be considered once all the above has been taken into account: the eye behind the eyepiece.

I find that on lunar and planetary that SCTs seem soft to me. However an aplanatic SCT like the Celestron Edge series does superbly well. Some individuals are much more sensitive to curvature of the field of view. I'm one of them. You might be too. Before making a purchase eliminate collimation and cool down as problems, etc.
I just read that for SCTs collimation has to be better then 99 percent. I would use the Lymax for cool down problems. Right click the image.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 8:45 pm
by notFritzArgelander
Refractordude wrote: Sun Feb 16, 2020 8:39 pm
notFritzArgelander wrote: Sun Feb 16, 2020 8:37 pm
Bigzmey wrote: Sun Feb 16, 2020 6:01 pm Tomcat, did you check collimation of your 8se? I had many refractors over the years from 80mm to 150mm, and none of them was better on planets than my 8" SCT.

If you want sharper views you should consider slow F10-13, or APO/ED refractors.
Bigzmey wrote: Sun Feb 16, 2020 6:01 pm Tomcat, did you check collimation of your 8se? I had many refractors over the years from 80mm to 150mm, and none of them was better on planets than my 8" SCT.

If you want sharper views you should consider slow F10-13, or APO/ED refractors.
I agree. There is almost no way an achromatic refractor less that 150mm is going to do as well on planetary contrast as an 8" SCT all other things being equal.

The things that need to be equal are: collimation needs to be right, atmospheric seeing conditions need to support the higher resolution from the 8", the 8" needs to be thermally stabilized.

There is one other factor that would need to be considered once all the above has been taken into account: the eye behind the eyepiece.

I find that on lunar and planetary that SCTs seem soft to me. However an aplanatic SCT like the Celestron Edge series does superbly well. Some individuals are much more sensitive to curvature of the field of view. I'm one of them. You might be too. Before making a purchase eliminate collimation and cool down as problems, etc.
I just read that for SCTs collimation has to be better then 99 percent.
99% of what? Collimation needs to be sensibly perfect. That isn't hard to achieve.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 8:53 pm
by helicon
Don Quixote wrote: Sun Feb 16, 2020 8:05 pm For visual the AR152 does very well on the lunar views for me. On DSO it is an absolutely wonderful tool. On the bright, concentrated Jupiter, and Saturn views it does show color. Mars is good. Venus is loaded with color. But keep in mind the EP you use can mitigate the color fringe issue. For imaging the planets I prefer my ES127 FCD100 APO. You will need to pick what you want most to view.
High power on the planets is highly dependent on your atmospheric conditions as you well know. When the atmosphere is less than great my 100MM f9 Skywatcher is the tool I go with.
I have an older Meade LXD75 8" SCT that performs very well on the planets.
If I were going to add to my kit and I had only an 8" SCT in my stable I would go with the 102ED.
The only thing I can't see well in the AR152 is Venus. Always shows some color fringes and appears, most of the time, to "boil" even when I can discern the phases. Pretty darn unimpressive object, or maybe it just magnifies the weaknesses of the scope being such a bright object.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 8:59 pm
by Refractordude
I found this to help with collimation.

https://starizona.com/tutorial/collimat ... assegrain/

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 10:31 pm
by Bigzmey
Tomcat, If you simply want to add a refractor to your collection, nothing wrong with that.

From this perspective I would suggest 102mm ED. The reason is that none of achro refractors you listed can compete with 8" SCT neither on DSOs or planets. Small ED/APO refractor does provide sharper views compared to plain SCT or a typical fast achro scope. Also, it does not need much acclimation and can be used as grab and go.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 10:41 pm
by Bigzmey
helicon wrote: Sun Feb 16, 2020 8:53 pm
Don Quixote wrote: Sun Feb 16, 2020 8:05 pm For visual the AR152 does very well on the lunar views for me. On DSO it is an absolutely wonderful tool. On the bright, concentrated Jupiter, and Saturn views it does show color. Mars is good. Venus is loaded with color. But keep in mind the EP you use can mitigate the color fringe issue. For imaging the planets I prefer my ES127 FCD100 APO. You will need to pick what you want most to view.
High power on the planets is highly dependent on your atmospheric conditions as you well know. When the atmosphere is less than great my 100MM f9 Skywatcher is the tool I go with.
I have an older Meade LXD75 8" SCT that performs very well on the planets.
If I were going to add to my kit and I had only an 8" SCT in my stable I would go with the 102ED.
The only thing I can't see well in the AR152 is Venus. Always shows some color fringes and appears, most of the time, to "boil" even when I can discern the phases. Pretty darn unimpressive object, or maybe it just magnifies the weaknesses of the scope being such a bright object.
Have you tried Venus lately Michael? It rides high at sunset now. You do want to use a filter to control the glare. Good quality blue filter seems to work the best, but I also had good results with Baader Sky & Moon Glow. With steadier atmosphere you can resolve some dark clouds near terminator.

Re: Explore scientific refractors

Posted: Sun Feb 16, 2020 11:05 pm
by helicon
[

The only thing I can't see well in the AR152 is Venus. Always shows some color fringes and appears, most of the time, to "boil" even when I can discern the phases. Pretty darn unimpressive object, or maybe it just magnifies the weaknesses of the scope being such a bright object.

Have you tried Venus lately Michael? It rides high at sunset now. You do want to use a filter to control the glare. Good quality blue filter seems to work the best, but I also had good results with Baader Sky & Moon Glow. With steadier atmosphere you can resolve some dark clouds near terminator.
I haven't tried a filter - a very good suggestion. Also I should check it out while it remains high after sunset. I suppose I also could dampen down the aperture a bit as well.

Re: Explore scientific refractors

Posted: Mon Feb 17, 2020 1:32 am
by DeanD
helicon wrote: Sun Feb 16, 2020 11:05 pm [

The only thing I can't see well in the AR152 is Venus. Always shows some color fringes and appears, most of the time, to "boil" even when I can discern the phases. Pretty darn unimpressive object, or maybe it just magnifies the weaknesses of the scope being such a bright object.

Have you tried Venus lately Michael? It rides high at sunset now. You do want to use a filter to control the glare. Good quality blue filter seems to work the best, but I also had good results with Baader Sky & Moon Glow. With steadier atmosphere you can resolve some dark clouds near terminator.
I haven't tried a filter - a very good suggestion. Also I should check it out while it remains high after sunset. I suppose I also could dampen down the aperture a bit as well.
The other option for Venus is daytime viewing. You don't have to wait until sunset! There is a big blue filter up there then... Even in my f5 150 achromat it usually looks quite sharp during the day. It is always difficult to observe any cloud features on Venus, even with filters, but the phases are easy during the day, and quite amazing when it swings back towards us and starts to get bigger with a thinner crescent.

Have fun,

Dean

Re: Explore scientific refractors

Posted: Mon Feb 17, 2020 3:02 pm
by Tomcat
Thanks for the replies, as for the 8se i think its mainly cool down problems as i dont stay out long enough for cool down. Have checked collimation by doing a star check and it looks right on. Looking at refractors because of shorter cool down times.

Re: Explore scientific refractors

Posted: Mon Feb 17, 2020 8:41 pm
by Bigzmey
Tomcat wrote: Mon Feb 17, 2020 3:02 pm Thanks for the replies, as for the 8se i think its mainly cool down problems as i dont stay out long enough for cool down. Have checked collimation by doing a star check and it looks right on. Looking at refractors because of shorter cool down times.
4" ED doublet would be a great choice for quick visual sessions. Have you considered Astro-Tech scopes?

https://www.astronomics.com/astro-tech- ... r-ota.html

Re: Explore scientific refractors

Posted: Mon Mar 02, 2020 12:59 am
by coopman
My vote is for the 4" ED scope too.