Sky-Watcher Classic 200P Dobsonian - what would you do if could choose your own "stock" eyepieces with all the experience you have now.

[amaury]

Hi all,

I always loved astronomy (I am in fact a geophysicist), and I bought my first telescope recently, a nice second-hand 200P Dobsonian from a member of this community. 

I am new to telescopes and related equipment.

So imagine you get an 8" f/6 dob but you get to choose your own eyepieces instead of getting the "stock" ones (so basically my case).

What would you do in that case? 

1- I assume the 25mm and 8mm BST StarGuider would be the most sensible approach hence the first option and then add a Barlow down the road.

2- In another post called "First eyepiece upgrade - what you wish you had done", people seem to recommend the Baader Hyperion Zoom.

So I guess the question is, what would do and why? Get a set of BST StarGuider EPs? or the Baader Hyperion Zoom? or would you do something else?

Thanks in advance for the advice.

Amaury

[Dark Vader]

I sort of did 1 & 2.

My 200p came with the 25 & 10mm. I then got a Starguider 7-21 zoom which was "fair" for a total beginner, and cheap. From that I got 3 Starguiders, the 25, 15 & 5mm followed by a Baader Hyperion 8-24 zoom and matching Barlow. 

The Starguider 15mm is my favourite of BST stable so far - nice and clear on the Moon at 80x. The 5mm gives 240x and some good views of Mars back in November. The 25 is "ok", marginally better than the stock EP.

The Hyperion zoom is just superb and Barlows very well as you might expect from a "matching" 2.25x Barlow. I've had that combo up to 337x on some Orion doubles. Definitely worth the money IMO.

Andy

[amaury]

Thanks for the input Andy.

The Hyperion zoom sounds great. Is there a downside compared to a fixed EP? For example, how does the 8mm in the Zoom compares to BST SG 8mm.

Amaury

[Second Time Around]

I'd very much recommend a zoom eyepiece as your workhorse.  One zoom eyepiece will cover multiple focal lengths and so is really excellent value for money.  

Despite having high quality fixed focal length eyepieces, I use my Baader zoom a lot more often.  The zoom plus a Barlow lens and a low power, wide field eyepiece is often all I use the whole evening.  Your existing 25mm eyepiece will fulfil the low power role to begin with.

Fixed focal length eyepieces may be slightly better corrected when compared with a zoom at the same magnification.   But that's not always a fair comparison as that magnification may not be the optimum for a given object.  This is because one of the many advantages of a zoom is to be able to dial in precisely the best focal length.  For instance, this may be 13mm or even 13.1mm, which may actually show more detail than shorter or longer fixed focal length eyepieces - even better quality ones.  

I particularly like the ability to increase the magnification to make use of brief moments of good seeing (a steady atmosphere).  It takes more time to swap out an eyepiece, and the opportunity may then be missed.  You can't see anything if you haven't got an eyepiece in the focusser!

Zooms also enable the field of view to be varied to frame an object to get the prettiest view.  For this reason I particularly like them for clusters.

Many of those who post here and advocate fixed focal lengths are experienced observers.  It's so easy to forget what it was like as a beginner!  A zoom eyepiece enables beginners to easily learn what difference a change of magnification makes on all the various classes of object.  It also shows them what focal lengths would be most useful to their eyes, their telescope, and their observing conditions.  They then have the option of buying/not buying the most appropriate fixed focal length eyepieces for them.  For these reasons I'd always recommend that beginners buy a zoom as their first eyepiece.

I'd supplement the zoom with a Barlow lens.  Just in case you're not aware, a Barlow lens multiplies the magnification of any eyepiece it's used with.  It goes in the focuser before the eyepiece.  The multiplication factor varies but 2x is most common.  Some of these 2x Barlows can also be used at 1.5x, although it's not always mentioned in the blurb, and it's one of these I'd recommend.  These dual 1.5x/2x Barlows allow the black lens cell to be unscrewed from the body of the Barlow and then screwed into the filter thread at the bottom of an eyepiece to give approx 1.5x.   First Light Optics do one in their Astro Essentials range that even has a standard T thread at the top for attaching a camera.  It's just £25.  Go to https://www.firstlightoptics.com/barlows/astro-essentials-125-2x-barlow-with-t-thread.html

The exact amplification varies from eyepiece to eyepiece depending on where the field stop is located.  At 2x amplification with the Baader zoom this will give you magnifications of approx 100-300x.  Most nights the seeing (atmospheric turbulence) won't be good enough to go as high as 300x and you'd get more use from the approx 75-225x that 1.5x amplification will give you.  Additionally, at a given magnification the field of view will be bigger with 1.5x amplification.  This is because the vast majority of zooms have a wider field of view at the high power end.

[Louis D]

Back in 1998 when I bought my 8" Dob, it came with no eyepieces.  I bought a 2" 38mm Rini MPL from the seller as a "finder" eyepiece, a 14mm Pentax XL for mid-range power, a 9mm Vixen LV for a bit more power, and a 5.2mm Pentax XL for highest power.  With my strong astigmatism, I had to buy long eye relief eyepieces, and the only options back then were the XL, LV, and LVW lines.  The XLs were $240 back in '98, which is about $390 apiece today.

[Spile]

I suppose the default eyepieces were chosen on the basis of keeping down costs but giving buyers the chance to see the difference between low and higher powers. I have no problem with the 25mm but the 10mm is pretty dreadful so that would be my choice for an upgrade. However that is going to be problematic as it will increase the price of a telescope that has just had a £100 price rise up even further. So maybe just drop the 10mm?

Sorry to be boring but I am very happy with my choice of Zoom, Barlow and Wide Angle. It is a lot of money compared to a couple of plossls  but the flexibility and convenience works for me.

[amaury]

Thank you all for your feedback.

2 hours ago, Second Time Around said:

A zoom eyepiece enables beginners to easily learn what difference a change of magnification makes on all the various classes of object.  It also shows them what focal lengths would be most useful to their eyes, their telescope, and their observing conditions. 

This quote from @Second Time Around is gold. The whole answer was very comprehensive, thank you very much indeed.  I have made my mind now. 

My 8" Dob came with the stock 10mm EP only (often referred to as "dreadful" just like @Spile said. Practically I have no eyepieces just like when @Louis D bought his Dob back in the days.

I'll keep my eyes open for a decent second-hand Baader Zoom. 

[Waddensky]

5 hours ago, amaury said:

The Hyperion zoom sounds great. Is there a downside compared to a fixed EP?

Other than the excellent points Steve mentions, the field of view of the Hyperion Zoom is a bit narrow on the longer focal lengths. That's why some people supplement the zoom with a good widefield eyepiece, the ES 24/68 or the 24 Panoptic for example. Other than that, I find the zoom very convenient and it works great with my ES 2x focal extender. The combination gets me in the 300x region for double star or planetary work.