Optimized for Astrophotography

in carbon tubus and extra rigid Octo60 focuser. Each Lacerta Photonewton is tested individually! It began as a project to offer a ready optimized Newtonian of affordable price, but having all necessary properties to deliver best images. It was developed through constant feedback, and now we have a well established brand on its own, used by the best and most active photographers here. Some references are given at the end. Here we explain the most important improvements we do:

Carbon Tubus - Made in Germany

Carbon is an ideal material for Newton tubes, but there are differences. Our tube maker Klaus Helmerichs has a long experience in producing lightweight but extremely stiff tubes, and developed his own techniques. Our tubes have the special feature to be more thick at the front and rear end, so tube rings from the shelf can be used. An importat point to save money, but no compromise on stability.

Velour - no baffles

Baffles can be very effective in suppressing stry light, but there are certain caveats. Cheap newtonians from far east tend to use baffles which are not properly calculated, but just put in in same distances and often let no more light pass than the primarys diameter. That means first, they introduce vignetting into the system. Second,  they are not working effectively, and third warm air rising from the primary must enter the light path every time it flows around a baffles edge. That may cause distortions, as air is not optically inactive. And fourth, the most important spot for straylight suppression on a Newtonian is the tube wall opposite of the focuser, from where reflected light can surpass the secondary and reach the chip directly. This is not covered at all by these baffles. We are using black velour to tape the complete inner tube wall, which is especially effective against strewlight entering in a shallow angle, where normal black matte paint is working less good. At the same time the contact between tube wall and air is buffered by the textile, so tube currents are prevented. And of course, the important spot opposite the focuser is blackened as well. Before applying, the self-adhesivevelour is being taped off, so loose particles and fibers are removed.

Octo60 focuser

Of course, the focuser is one main point in astrophotography. Same story here: Starting with a good and sturdy R&P focuser from the shelf, we built in ball bearings for the worm so it can not move back and forth, improving the mechanics. We replaced the original focuser tube with our own much thicker one, which has steel inlays for the 8 bearings. The inner diameter of the draw tube is brought to 50.9mm, so an inserted corrector cannot tilt anymore. The 8 bearings are made adjustable with pull and push screws at 90° angke too, and that at the same time stabilizes them. While movements are smooth and friction can be apllied, the draw tube is extremely stiff and cannot be bent by lateral weight up to 5kg, and out MFOC motofocus can stem a 8kg weight reproducable to 1 micron precision. To fix equipment we have made a centerlock clamp. So gear is rotatable, but stays on the optical axis and stability is literally like screwed down. Please consult Octo60 website for more.

a customers comment, too nice to hide it (Bernd Weinzierl):
Tommy, I just love this part !!! Perfect clamping, no tilt at all, no shifting, how could I ever live without it???

Secondary edge and rim blackened, bigger screws and steel plate

both edge and rim of the secondary mirror is blackened. Including the small chamfer that surrounds the aluminized mirror surface. Total reflection or no reflection, for best contrast, no straylight introduced there. The secondarys are glued to the holder, and not in a housing that may exert stress on the mirror at low temperatures. A secondary heater is available optionally. The collimation screws are steel, and a round steel plate beneath them from prevents grooving the secondary holder.

Primary rim blackened:

Advanced astro photographers are very critical, and a little secret to improve star halos is to mask off a small portion of the primary. That helps in softening diffraction artefacts from the clamps that secure the primary in its cell. At the same time it prevents stray light from the the primarys chamfer and mask off eventual edge zones. That very small scrifice pays off in practice!

Quality is scrutinized on each individual sample:

Each Lacerta Photonewton is tested individually, asserting the required position of focus, mechanical stability, ultimate precise collimation, and of course optical quality. No lemon optics will survive this tests!
We can deliver tests up to interferometric measurements of the whole system. We do not take this part easy, please refer to the test preparations and measurement

here you find some interferometric test reports

Collimation:

Up to now unfortunatly available in German only,  here is our worlds first collimation guide for photographic newtonians. How to achieve best stars up to the corners of your chip:
Newtonian collimation for astro photographers

we recommend:

For best possible star forms do not compromise on the corrector! In a package we offer our 4 lens coma corrector KomakorrF4, a Wynne style corrector that does not change the focal ratio at all, and deliver sharp stars across the field. The cheaper 2- lens correctos of Ross design introduce sperical aberration, and that softens stars not only in the field but also on axis. Compare yourself, open in two browser windows and blink back and forth - This comparison is courtesy to Burkhard K.:

www.teleskop-austria.at/info...4-lens-GYULAI.jpg
www.teleskop-austria.at/info...-2-lens-MPCC.jpg

some sample photos:

M51 10" f/4 Lacerta Photonewton by Tommy Nawratil
M45 (Rochus Hess mit FN2008c-flat und Gemini G53f)
Iris Nebula by Stefan Roth

specifications 10" f/4

weight: 12,5kg OTA without tube rings and rail
tube length: 915mm
focal position over tube: 142mm
secondary diameter: 82mm
100% illuminated field: 15mm
100% field with GPU KomakorrF4: 15mm
focuser over primary: 715mm
Mirrors are made of: Pyrex

Upgrades and special requirements:

we are open to do any upgrade on our Newtonians, for example we can offer them with TRUE 3" Feathertouch focuser and 3" corrector,
but be aware that these two parts alone cost approx. as much as the whole telescope in standard edition.
Adding other special requirements, like secondary heater, or different focal position for an optional reducer, is possible - just ask us.

visual observation:

Of course our Newtonians are fully usable for visual observation too. The standard edition is optimized for use with KomakorrF4 corrector, so the corrector just does not introduce vignetting the primary. You could use our visual back M48508 and insert your ocular. For compensating different eyepiece focal planes, it is possible to shorten the Octo60 by removing the Octo 12mm extension ring below the center lock, or adding more of those rings.

some customer opinions:

Michael Jäger:
I have the 10" since 25.000km in my car and never needed to recollimate. 
Norbert Mrozek:
You have made a fantastic instrument, I am totally excited. The first comet pics last night were convincing. All you promised was met point for point.

some selected references to visit:

Tommy Nawratil
Michael Schmidt
Rochus Hess
Herbert Walter
Jens Zippel
Markus Blauensteiner
Michael Jäger