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Does the GSO 15mm Super Plossl still has its years old field stop problems?

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#1 shubham_chandravanshi

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Posted 28 October 2020 - 10:59 PM

Hey guys I am from India. I recently got GSO 8" F/4 Imaging Newtonian Telescope. It has come with a 25mm 1.25" GSO eyepiece that gives 32x magnification. I have to buy eyepieces and barlows to have a wide range of magnifications. I know that this scope is meant for imaging purpose but I also do want to tease out some good visuals with it. For now, consider that I have the GSO 2" Coma Corrector as well, which has a 1.1x magnification.

I have decided to keep the eye relief in my eyepiece large and that's why I don't want to buy any shorter eyepiece than a 15mm (fl). For medium magnifications, I will use GSO 2" 2x Apochromatic Barlow with CC. And for high magnications, I will use 5x barlow with these eyepieces.

Now, the question is, which 15mm eyepiece should I buy? In India there is only one seller which sells products at reasonable prices, and it's tejraj.com . And there, I can only buy a 15mm GSO (I want Super Plossl, not Super View) or the 15mm Explore Scientific 52° 1.25" LER eyepiece (which is 3 times more expensive!).

I have read many threads on CN itself about the problems of the 15mm GSO Super Plossl eyepiece (I am talking about the specific ep not the whole Super Plossl series. There are many excellent reviews about 32mm GSO too.). I have read that the 15mm GSO do not have a field stop at all and even if it have it, it's in the wrong place. This creates a very blurry and diffused field stop while observing through it. (Please note that those threads were 7-8 years old, so things may have improved now)

 

Now, I want to know if anyone is using that GSO eyepiece. If yes, then does your eyepiece does the same as I explained above? Please let me know what do you think about it.

 

If that particular eyepiece do not have such problems, then I will buy that ep. But, if it still continues to have, I will have to go for the ES eyepiece. (My budget is not much high and I also cannot buy other eyepieces because they are a lot expensive here in India, that's why I am limited to tejraj.com only). I know that ES is not 3 times as good as a decent GSO eyepiece to justify it's price but, if the GSO 15mm has those problems, then it makes no sense to buy that, and thus I will go with the ES.

 

 

Please help me out with this problem! :)



#2 daniel_h

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Posted 28 October 2020 - 11:30 PM

don’t worry if it doesn’t have a field stop, they likely left off for either cost or to widen fov, you could make your own one out of thin card if necessary, some ep’s don’t have them, some users remove them, 



#3 shubham_chandravanshi

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Posted 29 October 2020 - 01:48 AM

But that would actually cause problems while observing. The observable field of view will diffuse into the field stop around the edges.

Anyone having the 15mm GSO eyepiece?

#4 peta62

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Posted 29 October 2020 - 02:34 AM

I do not have this particular GSO 15 mm, but I do have others and they are good. Not the top of the crop but great for the price. I do have the 32mm 2" and I really like it.

I am afraid you compromise the quality of your views by 5x barlow and I am not sure you need such magnifications, better to say I am not sure your seeing would allow it most of the time. I would use the scope for some time before deciding and ordering. You do not want to waste money on eyepiece you would almost never use.

I strongly recommend you to look for 2" eyepieces for focal lengths above 20 mm. I fully understand your price concerns, but you have invested money into a scope, so you should get the most of it now and it is not possible with 1.25" in lower magnifications.



#5 shubham_chandravanshi

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Posted 29 October 2020 - 08:27 AM

@peta62 yes you are right but:
1) at 266x, with 15mm and 5x barlow, I think I will be fine with seeing as 400x is the maximum theoretical magnification of my scope and 266x is well below it.
2) I am currently in 11th grade, and I belong to a very lower middle class family here in India. There was & is no way I could buy and own a telescope atleast untill I buy that with my own salary which is years ahead to happen. So, you must be thinking how did I get this scope!?
3) I got this scope for free! I am a subscriber of Chuck's Astrophotography channel and a few days ago, he uploaded a video in which he deliberately dropped his Celestron 8SE many times from 7-8 foot of height and destroyed it completely. And I just shared my feelings in the comments that although it was not in great condition but even that scope in "not so great condition" is a dream for many, like me. And I hope that one day through my hard work, I will be able to afford one and live the dreams I have seen.

This touched the hearts of many of them there and one very kind hearted person from Bulgaria, who is now my friend, said to me that he want to gift me a telescope! I literally cried. It was just so surreal and auspicious moment for me that I cannot stop my tears for many minutes... Then as we talked and conversed, he then finally ordered me a telescope from my country's local seller (tejraj.com) and that telescope is on its way to reach my home in a couple days.

As I didn't have any accessories with me, he said that he'll send me some of his, from Bulgaria. They are: an uncooled CMOS camera with sony imx178 color sensor (I don't know which brand), a focal reducer, a 5x barlow, etc.).

And to have some visuals, I decided that I will buy a 15mm ep and a 2" 2x barlow is all I need. I have planned a GSO Coma Corrector also but it is not for near future.

Regarding money, I don't have anything. I had saved around $300 since my childhood but seeing my father take such a big loan to buy our home, I gave him my savings. So to buy these things, I will need to borrow money from my relatives and friends. Unfortunately my parents are not on my support to give some money for that as they think that these things will distract me from my studies...

Anyways, hope you understand my situation. That's why I want to know from you, your advices. And regarding GSO eyepieces, I know that it has some very good ones like the 32mm you mentioned but I read that 15mm has many problems.....

🙏

Edited by shubham_chandravanshi, 29 October 2020 - 08:35 AM.


#6 peta62

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Posted 29 October 2020 - 02:35 PM

That is a really touching story.
Knowing the circumstances, I would wait with the coma corrector if I were you. Our eyes are often very forgiving and I just recently have seen a discussion ( not here, my home country, different language ), where they agreed people have huge differences in coma tolerance, so you will see how much it distracts you. I have Surplus Shed 2" 50 mm which already shows shadow of the secondary mirror on my C9.25, but I do not mind. It is a bit annoying on the Moon, but I do not recognise much it outside Moon and Sun. And coma corrector costs more than better eyepiece. Of course it is a different story with imagining, but you may correct it in post-production. Additional work, but seems to be less harm than to spend money on coma corrector immediately in your situation.
If the only problem with GSO 15mm is the missing field stop, I agree with daniel_h. Missing field stop only widens the FOV and you can easily make the field stop if you want. Let me know if there is any other problem, I can try to find out, but it would take time ( weeks due to Covid  ).
How are your plans considering collimation ? I am afraid you will have to on a fast Newton.



#7 daniel_h

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Posted 29 October 2020 - 04:22 PM

i don’t know you’ll b able to use the 5x barlow too often, 266x mag is reasonably high -you will need great collination skills for your f4 scope to handle that magnification -worry about that first




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