Eyepieces for a SW 250 dob

[CLOUD90]

Hi all I’m a newbie to all this and have just brought a skywatcher 250p Dobson 

but only have a 2x Barlow and a 25mm eye relief 1.25  lens I’m guessing it’s a standard one that came with it any suggestions on what kind of eye pieces sizes etc would be ideal for viewing planets  only got it 2 days ago lol so I’m very new and don’t really want to spend to much on the wrong things 

[joe aguiar]

There r so many companies with 3 to 5 lines of eps that can be a good up from the ones that come with it

I think any plossls  or super plossls will be better, like omni super plossls 

Meade 5000 HD 60 are ok

Es has least 3 sets of eps 82 68 50 eps

Bst seem to be popular however I dont have those

Tele vue would be better corrected in a f5 scope but cost alot altho TV has plossl line

U can try used market get really good quality for good price since they used

If u can find used TV radian on used market u may find for 80 each which is really good.

Joejaguar 

 

Edited March 20, 2020 by joe aguiar

[John]

If you want something that improves on what came with the scope but does not cost a fortune the BST Starguiders are well thought of on this forum

https://www.firstlightoptics.com/bst-starguider-eyepieces.html

For planets I would suggest the 8mm or 5mm focal lengths or alternatively the 12mm which you could use with your 2x barlow lens to give a 6mm equivalent.

 

[RT65CB-SWL]

Hi @CLOUD90 and welcome to SGL. 

+1 for the TeleVue Radian, (now discontinued and superceded by the DeLite's), I have the 6mm. Radian's have 60deg AFOV, (DeLite’s have 62deg AFOV). Nagler's are nice too at 82deg AFOV. They are a bit more expensive than Radian's or DeLite's.

If you want to go for a zoom e/p, then these. First off is the Nagler 3-6mm zoom, though it only gives 50deg; and then there is the Baader 8-24mm Mk llI or MkIV Zoom gives 68deg AFOV and can be used in 1.25" or 2" drawtubes. The earlier Mkl & Mkll zooms were fairly heavy. 

Pssst! - want a budget zoom e/p? ...the Seben 8-24mm, (not to be confused with its 7-21mm sibling)... apparently it is very good...  unlike other Seben 'scopes & e/p's, (which is pretty much crap/$#!t).

Edited April 5, 2020 by Philip R

[Paul73]

Another vote for the BST Starguiders. I used them happily in my 10” f4.7 Dob.

Then the £££ Televue bug hit.....

Paul

[CLOUD90]

Thanks all  I think I’m going to try the bst  starguiders 12mm  with the 2x Barlow for now  would it be worth investing in a x3 Barlow ? And also  maybe a dumb question lol I can only apologize is it the small the mm the greater the zoom ? 

[Louis D]

1 hour ago, CLOUD90 said:

Thanks all  I think I’m going to try the bst  starguiders 12mm  with the 2x Barlow for now  would it be worth investing in a x3 Barlow ? And also  maybe a dumb question lol I can only apologize is it the small the mm the greater the zoom ? 

Correct.  Just divide your scope's focal length (1200mm) by the eyepiece focal length (12mm for instance) to get the magnification (power) of 100x.  Obviously, a bigger denominator (eyepiece focal length) yields a lower power.  As the focal length drops, the power rises in bigger and bigger jumps.

[Ricochet]

7 hours ago, CLOUD90 said:

would it be worth investing in a x3 Barlow ?

Not really. The 5, 8 and 12mm Starguiders are the ones I think are suitable for use with an f5 scope. With a 2x barlow that will cover all your high power needs, you could probably even get away with 8, 12 and 2x barlow. 

[John]

The 3x barlow would give you too much magnification to be much use. Stick with a 2x.

 

[CLOUD90]

Cool thanks I see a lot of 30-40 mm with  high degrees on eBay what are these normally used for ? 

[John]

1 hour ago, CLOUD90 said:

Cool thanks I see a lot of 30-40 mm with  high degrees on eBay what are these normally used for ? 

Longer focal length eyepieces with wide fields of view (the degrees figure) are for low power, wide field observing. With your scope 30mm - 32mm is around the longest focal length eyepiece that is effective.

The 2 inch size eyepieces give you an even larger view but the low cost 2 inch wide angle eyepieces dont work that will with the F/4.7 focal ratio of the 250mm dobsonian - you tend to get distortions in the outer parts of the field of view.

The 25mm BST Starguider will show nearly as wide a field as a 1.25 inch eyepiece can in a scope so there is not a lot of point in getting anything with a longer focal length unless you move to the 2 inch fitting.

 

[Ships and Stars]

You are spoiled for choice really. Much more widefield and not a planetary eyepiece, but if you are looking for mega-budget EPs, the bog standard 28mm 2" SW eyepiece is cheap as chips and actually ok and great for lunar. Someone might even give you one as they come standard with different SW scopes and usually get chucked in a desk drawer. The eyecup is very comfortable and adjustable. Sure, it has some coma on the edges in faster scopes, but it didn't bother me for almost a year until I became pickier! I also bought some second-hand13mm and 8mm Celestron plossls for something silly like £7 each and have 2x barlowed them on Venus a few weeks ago when seeing conditions were very stable. They are also decent in my book. The Seben 8-24 zoom is another bargain, I have one and it allows you to quickly zoom in to the limit of the sky conditions, good for planets I suppose. Beyond eyepieces, accurate collimation of the secondary, then primary mirror is critical. After this, giving the scope time outside to cool down outside so heat thermals don't rise off the mirror and blur things is as important as anything else, especially for high mag viewing. An 8" scope shouldn't take too long to cool down if stored inside, and virtually no cool down time if stored in unheated shed etc. 

[CLOUD90]

I do have a 2inch adapter but I think I’m gonna stick to the 1.25 lens  atm as I’m new to astronomy and to all the equipment lol would it also be worth investing in some filters planetary,lunar ect  I live in the cotswold in the middle of nowhere and get great clear skies a lot of the time Lol typical as soon as I purchased the telescope I haven’t been able to use it yet as it’s been cloudy the past couple of days 

[Ships and Stars]

1 minute ago, CLOUD90 said:

I do have a 2inch adapter but I think I’m gonna stick to the 1.25 lens  atm as I’m new to astronomy and to all the equipment lol would it also be worth investing in some filters planetary,lunar ect  I live in the cotswold in the middle of nowhere and get great clear skies a lot of the time Lol typical as soon as I purchased the telescope I haven’t been able to use it yet as it’s been cloudy the past couple of days 

It's always cloudy for at least a few days anytime someone buys new astro gear! Sounds like you have good conditions there, I'm sure you'll have a bash soon. Get that collimation accurate if things don't look nice and sharp at lower magnification! It's a little complicated at first, but becomes second nature once you've done it a few times. Once the secondary mirror is adjusted, it usually stays put, the primary mirror will perhaps need more frequent checks, but can stay well collimated for long periods if the scope isn't bumped around to much. A 250p will show lots of interesting DSOs as well as planets. Enjoy! A good forum here btw, they've helped me immensely.

[CLOUD90]

Thanks yeah I collimated it yesterday watched a great simple video on YouTube as it came with a laser Tool manage to do it In a few minutes I do need to set the finder scope up properly Tho The Seben 8-24 zoom this sounds cheap and cheerful ?

[John]

1 hour ago, CLOUD90 said:

Thanks yeah I collimated it yesterday watched a great simple video on YouTube as it came with a laser Tool manage to do it In a few minutes I do need to set the finder scope up properly Tho The Seben 8-24 zoom this sounds cheap and cheerful ?

Getting the finder scope aligned with what the main scope is observing is really important. It will be very difficult to find things without this having been done fairly accurately.

You can use a distant object in daylight to do this. Something like a TV mast or a chimney around 1km or more away as an alignment target.

The Seben 8-24 zoom is quite good for its price. The field of view is quite narrow at the 24mm end though.

 

[CLOUD90]

Lol unfortunately I live in area Surrounded by acres and acres of woods fields etc. the little village has around 20houses In a little cul-de-sac with no street lights I might be able to find a telegraph pole far enough to do it maybe ?

[Ships and Stars]

1 minute ago, CLOUD90 said:

Lol unfortunately I live in area Surrounded by acres and acres of woods fields etc. the little village has around 20houses In a little cul-de-sac with no street lights I might be able to find a telegraph pole far enough to do it maybe ?

Venus is a good target to use for finder alignment this time of year if you do it at night, because it's almost painfully bright though a scope and impossible to miss once it's near the eyepiece. Venus or any really bright star that's kind of isolated will do. Capella in Auriga is another good one to use for alignment, there's no mistaking it for the fainter stars immediately around it. 

[John]

1 hour ago, CLOUD90 said:

Lol unfortunately I live in area Surrounded by acres and acres of woods fields etc. the little village has around 20houses In a little cul-de-sac with no street lights I might be able to find a telegraph pole far enough to do it maybe ?

As long as its a good way off the target does not matter.

[Timebandit]

 

 

The BST Starguiders have a good reputation on this site. So would be the ideal upgrade in eyepiece, without breaking the bank

As I see you are a newbie, I would also recommend you get the book "Turn left at Orion" this will give you a great start into locating some objects/DSO in the night sky.

 

Have fun 🔭

 

 

 

[John]

39 minutes ago, John said:

As long as its a good way off the target does not matter.

Actually, on 2nd thoughts, flying birds are not suitable targets !

[joe aguiar]

5 hours ago, CLOUD90 said:

I do have a 2inch adapter but I think I’m gonna stick to the 1.25 lens  atm as I’m new to astronomy and to all the equipment lol would it also be worth investing in some filters planetary,lunar ect  I live in the cotswold in the middle of nowhere and get great clear skies a lot of the time Lol typical as soon as I purchased the telescope I haven’t been able to use it yet as it’s been cloudy the past couple of days 

Moon filter is good

Forget planet filter

2x Barlow over 3x

I'll send u a link y planet golter not always great

Joejaguar 

[CLOUD90]

Hi all recently had my first go on the dob last night using  the only eye piece I have atm which is a super 25Mm wide angle long eye relief pointed at Venus could see what looked be a bright tiny moon is that normal for that size of eye piece ? 

[John]

That's what Venus currently looks like. Its at around 50% phase right now so will look like a tiny version of a half phase moon.

The 25mm eyepiece is delivering magnification with your scope of 48x which is quite low power.

 

[CLOUD90]

Thanks John I will be investing in a new eye piece when I get paid  still not sure which one I’m going to get yet lol there’s to many