Long Perng 90mm f5.5 APO on its way.

[casstony]

Hi Laurie, thanks for the info and welcome to IIS. It probably is the same scope as the Megrez 88 but they've squeezed a couple of extra mm's out of the objective - nice little visual scope in any case.

Tony

[Larryp (Laurie)]

Certainly is Tony. Thanks for the welcome!

[Larryp (Laurie)]

Hi Tony-just had email from Long Perng confirming LP90 mm and Megrez 88 mm use the same lens

[casstony]

It's interesting that LP will provide info about glass types; WO is more coy about the objectives in their scopes. The Megrezz 88 wasn't available for very long so I'm curious to see if the repackaged LP is more popular.

I just tuned up the focuser on the used Megrez 88 I bought - pulled it apart to find out why the dual speed wasn't working and it turned out I only needed to tighten a grub screw - works like a new one now.

[Larryp (Laurie)]

Hi Tony-have you tried planetary observing with your Megrez? I have not had good enough seeing conditions as yet, to really evaluate the LP, but I just have a feeling it is not quite there for this purpose. I will wait for better conditions to be sure. Could not see any features on Mars, but seeing terrible, and Saturn looked better, but could barely make out Cassini division. Lunar views are tack-sharp, even at 200x

[Larryp (Laurie)]

Long Perng seem very open about their designs. I called the factory to find out about the glass used, and the lady I spoke to took my email and said I would hear from them. Shortly after I received email with an attachment from their catalogue showing the specifications for their 80mm and 90mm scopes. I replied to the email asking if this lens was the same as Megrez 88mm, and received a confirmation that it is indeed the same lens. I anyone would like to see the catalogue page, please supply an email address and I will forward it.

[casstony]

Originally Posted by Larryp

. Could not see any features on Mars, but seeing terrible,

I've only had one chance to look at Mars and that was at 100x in poor conditions - light and dark areas were still visible, though not as obvious as in an 8" SCT I had out at the same time. That's to be expected though; I find a larger scope almost always shows a better image regardless of the conditions, with better contrast and colour saturation.

When testing a scope I prefer to have another out at the same time to compare the views - avoids being tricked by not taking into account one variable or another.

[Larryp (Laurie)]

Thanks for the advice Tony. I used to have a Televue Pronto years ago, while I was waiting on delivery of AP 6" Starfire. Pronto was amazing-could use 200x on Mars and clearly see polar cap and surface markings, and I guess I am remembering that when evaluating the LP.

[casstony]

Thanks for the catalogue Laurie. That's the first time I've seen a manufacturer supply details of the glass types used. It's interesting that the LP 80 to 100mm (and megrez 88) doublets all use the same glass type for the mating element (NBM51) and it's not a cheap glass, it's price being in the same range as FPL51.
http://www.oharacorp.com/pdf/glass-chart-2012.pdf

[Larryp (Laurie)]

Obviously not a cheap lens Tony. Thanks for the glass chart

[Per Johansson (Per)]

Originally Posted by casstony

Thanks for the catalogue Laurie. That's the first time I've seen a manufacturer supply details of the glass types used. It's interesting that the LP 80 to 100mm (and megrez 88) doublets all use the same glass type for the mating element (NBM51) and it's not a cheap glass, it's price being in the same range as FPL51.
http://www.oharacorp.com/pdf/glass-chart-2012.pdf

Hi all!

I have been looking for glass info about the LP 100 F/6 doublet. Some places on the web lists it as FPL-51 and others as FPL-53. Was that in the details supplied by LP?

BR

/Per Johansson

[casstony]

Hi Per, the LP 100 f/6 doublet uses FPL51 + NBM51, so it should have similar performance to the 90 f/5.5, nice visually but not ideal for imaging. Welcome to IIS

[Per Johansson (Per)]

Thanks! It seems logical that the 100 should use the same glass as the 90 as it is not much more in price.
I have seen reports that the 100 has visually similiar ca correction as the Skywatcher ed 80 so I guess it is the mating glass that makes it so good. I have also seen a startest were it looks like the megrez 88 and 72 show less ca than the United optics/Kunming 102 F7 (Astro prof/Starwave/Ikharus/Orion) and 70 F6 (TS):
http://www.teleskop-austria.at/infor...pochromats.jpg
I want it both for visual and photo. The few images I have seen have been through mono cameras with rgb filters so the CA will not show.

[Larryp (Laurie)]

Hi Tony-I said before I wasn't sure about my LP90. Finally determined the lens wasn't as good as it should be, and exchanged the scope. New one is excellent-great star images and good planetary resolution. I was interested in your comment that LP90 is a good visual scope, but not so good for imaging.
My astrophotography goes back to the hypered film days, and since I have been out of the hobby for 15 years or so, I am not yet familiar with modern CCDs.
I would like to get a colour ccd camera at some stage, but I notice the LP90 has some ca at the red end on bright objects, so does this rule it out for colour ccd imaging?

[casstony]

Glad to hear you got a good scope Laurie - did you determine if there was a particular aberration or lens assembly problem with the first one?

My comment about imaging was just a general one based on this being a fast fpl51 doublet - I have to focus very precisely to get views with no apparent CA and I imagine a colour CCD would be less forgiving.

[Terry B]

Originally Posted by Larryp

Hi Tony-I said before I wasn't sure about my LP90. Finally determined the lens wasn't as good as it should be, and exchanged the scope. New one is excellent-great star images and good planetary resolution. I was interested in your comment that LP90 is a good visual scope, but not so good for imaging.
My astrophotography goes back to the hypered film days, and since I have been out of the hobby for 15 years or so, I am not yet familiar with modern CCDs.
I would like to get a colour ccd camera at some stage, but I notice the LP90 has some ca at the red end on bright objects, so does this rule it out for colour ccd imaging?

I would ahve thought almost the opposite.
A 90mm scope of any type will only give dim views visually due to the limited light collection.
For photos with a monochrome CCD then you would just need to focus slightly differently for the blue channel.

[casstony]

Originally Posted by Terry B

I would ahve thought almost the opposite.
A 90mm scope of any type will only give dim views visually due to the limited light collection.
For photos with a monochrome CCD then you would just need to focus slightly differently for the blue channel.

The 90mm scope doesn't do well for close up views of DSO's. The C11 isn't so good for quick looks or wide fields. Different scopes for different jobs although I'm currently a bit overstocked with 3.5, 6, 8, 10 (and 12" in the mail) apertures.

I'm sure even colour CCD images through the scope would look nice, depending on how nit-picky one is about CA.

[Larryp (Laurie)]

Thanks for you views tony and Terry. I have seen some very nice rich field images taken with small short focus refractors, and I accept they won't be much use on something like a galaxy. Just wanted an opinion of the imaging capabilities of a LP90.
The first scope suffered from too much spherical aberration

[brian nordstrom (As avatar)]

Thanks Petra , I ordered my new Atik 314E CCD from andrews today , it will be here early next week , Now its just the learning to ,,, well , learn . how to drive it .
My 1st CCD camera..
I will keep you all posted .
Brian.

Originally Posted by spacezebra

Hi Brian

Many thanks for posting these pics - Ill be watching with keen interest on your astrophotos. Im still keen on the orion but as said earlier could be persuaded otherwise.

Cheers Petra d.

[Larryp (Laurie)]

Hi Brian
I have a LP 90mm as well, so I will be very interested to see photos with your new camera. Best wishes