Eyepiece set for a Perseus 150 F/12

[ukjohn]

Having owned the Perseus 150 F/12 for some months now I've got to know it's "little ways" reasonably well and this has led me to the conclusion that I needed to put together a set of eyepieces especially tailored to this scope.

My normal eyepieces comprise Tele Vue from the 31mm Nagler, 21mm, 13mm, 8mm and 6mm Ethos then a mix of Pentax XW's and Tele Vue Radians for the 5mm, 4mm, 3.5mm and 3mm focal lengths. I also have a 2" 2x Tele Vue Powermate. It's a great set for my other scopes which range from a Vixen ED102 F/6.5 to an Orion Optics (UK) 12" F/5.3 dobsoninan. The rather large weight variations in the set don't sit well with my long tubed Istar 6 inch though because the weight variations (2 lbs to a few oz's) create vibration and balance issues galore as I change eyepieces.

So I've set about finding a small set of decent quality eyepieces especially for the big Istar refractor with the aim of delivering a useful range of magnification and field of view while maintaining relatively even weight per eyepiece. The set I have come up with comprises:

* 31mm Baader Hyperion Aspheric: used in 2" mode it delivers a true field of view of 1.25 degrees @ 58x magnification.

* 24mm - 8mm Baader Mk111 Zoom: The 24mm setting is rather narrow but from 20mm to 8mm the field is well defined and the optical  performance very good. This one eyepiece covers the 75x to 225x range of magnifications. Again I use this eyepiece in it's 2" mode and it's weight is close to that of the 31mm Aspheric.

* 6mm Vixen Lanthanum: Although only delivering a 45 degree apparent field of view this eyepiece is very sharp, has a really comfortable 20mm of eye relief and delivers a nice top end maximum magnification of 300x. I use the eyepiece in a permanently fixed 2" adapter which takes the overall weight to around the same as the Aspheric and the Zoom eyepieces.

So a 3 eyepiece set can, I hope, serve the Perseus 150 F/12 well as well as minimising the disturbances when changing oculars.

At least, thats the theory 

[rgm]

I am curious as to what mount you are using. I have my 5" f12 on a Losmandy G11. This allows me to tighten the friction on the RA and Dec to a point where it is usable. I do agree with you about the problems different weigth EPs cause. Without enough tigthening, my scope will take a nose dive.

[astromanuk]

When I was using my old 6" f/15 refractor I had a small collection of plossl eyepieces that I used exclusively with this telescope. It was before the days of the mass explosion of wide angle eyepiece designs. I had a 50mm 2" Clave as my low power and found that pinpoint stars to the edge of field and inky black sky background were so enjoyable, I never considered searching for a wider field eyepiece. The great thing about the plossls was that even the 2" versions didn't weigh enough to alter the telescope balance.

[ukjohn]

Jun 5, 2014 5:22:31 GMT -5 rgm said:

I am curious as to what mount you are using. I have my 5" f12 on a Losmandy G11. This allows me to tighten the friction on the RA and Dec to a point where it is usable. I do agree with you about the problems different weigth EPs cause. Without enough tigthening, my scope will take a nose dive.

Hi Bob,

My mount is a Skywatcher EQ6 head mounted on a Meade Giant Field Tripod - the one with 3 inch steel tubed legs. The scope and mount connection is via a Losmandy plate. I don't have the funds for a G11, alas. It does the job but a tube of this length is going to challenge any mount unless it's of the mega-heavy duty observatory type I reckon. My aim has been to keep the set up moveable if not actually portable !

[jimcurry]

For my average night with most any scope I use a TEC rotating diagonal (turret) with 5 eyepieces. I generally use a set of parfocal eyepieces. I may keep my N31 mounted in a prism diagonal for a finder eyepiece. It weighs the same as the turret assembly so there's no rebalance issues to deal with. I do have to hold the focuser while making the change to prevent a nosedive. Here's my custom build Istar 6" f/12.

Jim

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[ukjohn]

Thats a lovely looking scope Jim 

I have wondered about using a turret with my 6" F/12. Baader do the Q-Turret set for quite a reasonable price which includes their 3 classic orthos and a 32mm plossl plus the 2.25x / 1.3x Q-Turret barlow.

Keeping the weight changes to a minimum at the eyepiece end does help maintain scope stability.

[rgm]

I have the Baader Q-Turret and barlow and use them with my Konigs and Orthos. If I use a 5/4" diagonal, the weight is similar to a 2" diagonal and heavy 2" EP. The turret is made of a type of plactic, but works well.