Jump to content

 

1825338873_SNRPN2021banner.jpg.68bf12c7791f26559c66cf7bce79fe3d.jpg

 

Sky Watcher 200P EP's


Recommended Posts

Hi,

Does anyone know what the 10mm and 25mm EP type is that comes with the Explorer 200p? I've looked on the EP's and there seems to be no markings on them to indicate the type of EP.

I was using the EP (and a moon filter) Sunday night to look at the moon. With the 10mm and 2x barlow the FOV was tiny - Like looking through a keyhole. I read in the tutorial section that some EP's types can give this.

Are wide FOV EP's expensive and can you get them at 10mm?

Link to comment
Share on other sites

  • Replies 37
  • Created
  • Last Reply

Top Posters In This Topic

they are plossl's. the 25mm is ok; the 10mm is not great. You can get wider field (up to 100 deg; yours is about 52) but they get very very expensive. IMHO, a decent compromise is the planetary eyepieces shown here which I think give an AFOV of 60something degrees. I think they do a deal if you buy two.

Weitwinkelokulare 1,25" ab 60° - Teleskop-Express: Astro-Shop + Fotografie + Naturbeobachtung

Link to comment
Share on other sites

Ah, I see, so they are no good for high mag?

I have noticed every now and then a black circle in the middle of the fov. I read that it is something to do with the exit pupil - In the post by Andrew "Understanding and choosing eyepieces" in the Primers and Tutorials forum.

Could anyone elaborate on this please?

When I put my camera to the EP Sunday night to try taking some photos I noticed it whilst looking at the camera's lcd.

Link to comment
Share on other sites

it's not that they are no good for high mag, it's just that they are unnecessary for high mag.

if you scope aperture in mm divided by magnification (with a particular e/p) is more than about 7 then the exit pupil may be too large and you start to see the shadow of the secondary mirror (i think)

Link to comment
Share on other sites

Ah, I see, so they are no good for high mag?

I have noticed every now and then a black circle in the middle of the fov. I read that it is something to do with the exit pupil - In the post by Andrew "Understanding and choosing eyepieces" in the Primers and Tutorials forum.

Could anyone elaborate on this please?

When I put my camera to the EP Sunday night to try taking some photos I noticed it whilst looking at the camera's lcd.

The exit pupil is the bundle of light rays that comes out of the eyepiece and into your eye. It's diameter (expressed in mm) varies with differenct eyepiece / scope focal length combinations. Generally 7mm is the maximum useful exit pupil size because your fully dilated pupil is around that diameter (getting smaller with older eyes). Hold up some binoculars to the light and look at the eyepieces from several inches away and you will see the exit pupils as two circular patches of light. A good guiline with your scope would be to go for 32mm eyepieces as your lowest power - longer focal lengths than this (eg: 40mm etc) will give you an overlarge exit pupil and the secondary shadow might be an issue. The 2" format eyepieces have wider fields of view which is why they are popular.

The black circle in the middle of the FoV sounds like you are seeing the outline secondary mirror which you should not be seeing if the scope is properly in focus. If you get a star in focus it should be a tight point of light - de-focus it slightly and it will expand into a disk of light with a black spot in the centre (a bit like a polo mint !) - that is the "shadow" of your secondary mirror and if the scope is in good collimation it should be in the centre of the de-focussed star disk.

Edited by John
Link to comment
Share on other sites

Ah, yes that is exactly what I see, when in foucs the stars are pin points of light, when I did unfocus I got the polo effect with the black centre circle in the middle of the white circle.

I only saw the black light when putting a camera to the EP to try and take some photos of the moon. Maybe the camera's focal length or lens caused this?

Link to comment
Share on other sites

they are plossl's.

I had an Explorer 200P but the eyepieces that came with it werent Plossls ( it was the latest black diamomd OTA)

Are the eyepieces very light and look like these?

4306403681_f7e9a26ed5.jpg

if so, then they are Modified Achromats. They are a lower quality than Plossls and are best used at low to medium power in small to medium size telescopes, ie, 200mm. This could explain why you got poor performance with a Barlow.

If you dont want to spend a lot and dont want to go for wide angles ep's, Skywatchers Super Plossls are very good and inexpensive. I had the 10mm with and without a barlow ( x2) on my 200p and got great sharp views of the moons surface and could split the Double Double easily in good seeing.

Allan

Link to comment
Share on other sites

Had a look at the moon and mars last night, my first look at mars, it was quiet small even at 200x. The 10mm EP is like looking through a keyhole.

What would be a good mid range EP considering that my scope is a f5 reflector?

Thaks for the advice.

Link to comment
Share on other sites

Yes, they are the ones. I find them very good quality and at that price, you cant really go wrong.

I am not sure how good the barlow is, i never used it. Orion Shorty barlows are very good, Orion Shorty plus is supposed to be even better. I would spend as much as you can on a Barlow if you want one, if you get a cheap one, it doesnt matter how good your ep's are, they will perform worse with a low quality barlow.

Also, look for used Televue plossls, they are good prices for one of the best Plossl designs around.

The Revelation range of eyepieces are good quality too, look at what Telescopehouse has to offer. They also do Wide Angle Plossls at good prices, although i dont knbow how good they are. Their Revelation Photo-Visual Eyepiece and Filter Kit looks a good deal too, as does Tophouses recommendation.

I think you must be prepared to swap and change eyepieces around for a while till you discover your ideal selection!

Allan

Edited by alfingido
Link to comment
Share on other sites

Had a look at the moon and mars last night, my first look at mars, it was quiet small even at 200x. The 10mm EP is like looking through a keyhole.

What would be a good mid range EP considering that my scope is a f5 reflector?

Thaks for the advice.

Mars is a small object - I was using 330x a couple of nights ago and it still does not appear that big. After 29 January it's going to start apprearing smaller quite rapidly as well so this is about as good as it's going to get this time around.

200x is more than enough for your scope to show all the detail it can though - my most often used power on planets is 170x even with my 10" scope.

When you say "mid range" do you in mean price / quality or focal length / magnification ?. If you think your 10mm is "keyhole like" then wide field eyepieces might be for you.

Link to comment
Share on other sites

Just a remark on wide angles for high magnification: they do make sense, but come at a price. I use an ultra wide angle at 140x which is ideal for e.g. planetary nebulae. For planets they make less sense, but 60deg still lets you find your object faster. If your reflector is F/5 then a 5mm is in order to reach optimum magnification (given good seeing). A 10mm with a good barlow is also an option.

Mars is a hard object, and requires some time to spot all the details.

Link to comment
Share on other sites

Just come in for a warm, it's freezing out there, but i can now say for a fact there's a definite visual difference between the antares kit ones I linked above and the 10mm that comes with the 200p. Actual clarity is better and also the antares one seems to keep it's clarity right across the field of view whereas the 200p one doesn't, i'm only a noob so don't know the technicalities, but the 10mm that came with the skywatcher was a like slightly out of focus on the outside circle but the antares one wasn't. definitely an improvement with the antares, really glad i bought them. They're actually quite a bit heavier than the skywatcher ones too.

Link to comment
Share on other sites

Just looked at the Barlow lens that comes with the 200p and it looks like it has a single lens. Just checked the OVL web site and specs for the 200p on EQ5 mount states "x2 Deluxe Barlow Lens 1.25" (with Camera Adaptor) "

On the OVL web site the Economy Barlow is :-

"x2 Sky-Watcher 1.25" Economy Barlow (Single Lens) "

The Deluxe Barlow is :-

"x2 Sky-Watcher 1.25" Deluxe Barlow (Double Lens) "

Well I'm sure my Barlow only has a single lens - Does anyone else with a 200p have a single lens barlow?

May call OVL today and find out.

Edited by SkyExplorer
Link to comment
Share on other sites

I dont have this barlow anymore, but generally, eyepieces ( and I suppose Barlows) have lens elements sandwiched together. You may only see one piece of glass but it may have two lenses.

If I were you, I would look out for a good barlow in the for sale section or on Astro buy and sell then you will know exactly what you have.

The supplied Barlow is only a basic one, upgrading is relatively cheap.

Allan

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.