alacant

They are also used (to induce flex and movement!) in the base of the assembly.

Here's hoping. The usual rule is: So you're sort of half the way there. But hey, at this game pragmatism rules. EDIT: Oh, almost forgot... WARNING: the GSO cell. You may have noticed that the black-knob mirror tilt screws can me adjusted so that they bear against the underside of the mirror (sic). You may want to put washers to prevent their clockwise motion allowing metal to glass contact. In fact I'd say it's essential.

Yeah. Loadsa confusion. It's important to distinguish TS' version from the fixed flanged version. The latter will not thread. HTH

That is for the TS'-GPU. Cheers

https://siril.org/ Lose: get rid of. Don't include. Without. Forget.... etc. It's the offset on the 600d :

https://siril.org/ Lose: get rid of. Don't include. Don't use dark frames. Forget.... etc. The 600d's offset:

Hi. Are you sure the tilt is not caused by the rubber washers in the focuser? Seven in total. Cheers

Hi So many issues are solved by their removal; convert a bottom of the range reflector into an autograph. I wonder if you could help answer a question I am asked often. What was the silicone you used? Source, type... etc. I have no knowledge of non-Spanish brands. A photo would be great. Cheers and TIA

I only know the Spanish version which I translate as 'neutral silicone sealant'. The 'A+' may help identify what it is. HTH

Hi No. Only the high end TS e.g. the ONTC range, are. The economy TS-gso mirrors just rest on cork pads in an ill fitting cell. This is one of the reasons they lose collimation so easily. Lovely shot. With stars like that, you'll get an excellent m5, Good luck and do post if you have a go.

Great news. If you want even better, simply remove the clips and the ring. The mirror is then held in the cell using silicone. This has the added advantage of preventing lateral movement of the primary mirror and so helps collimation hold at all tube angles. Cheers

Hi The star you chose is not suitable for guiding and especially not for the guiding assistant. Best to allow PHD2 to select a star. But by far the best way to solve backlash issues is to dismantle DEC, clean, re-grease and adjust. This is especially true on new mounts direct from the factory. That software stand a chance, mass produced mounts need to be as mechanically perfect as you can get. There's a DIY kit with the parts and guidance you need. If however you're not going to fix the mount, then the only way to tame 9000ms of backlash would be guiding DEC south only. Cheers and HTH

Hi Unlike a guide telescope, the focus of the guide camera on an OAG benefits from being as close to perfect as you can get it. Focus the main camera on e.g. a clump of trees or buildings (it doesn't need to be at infinity) and clamp the focuser. You'll need very low gain on both cameras with the 200p tube cover in place, but with the cap on the removable smaller aperture removed. Without touching the focus position you just set, bring the guide camera to focus upon the same object. ZWO provide a nice bin2 in firmware, before the image is downloaded. Recommended, but don't forget to create a new guide profile and dark frame for the bin. Repeat the process at infinity on a star field knowing that you're now very close to the exact parfocal distance. Anywhere in Cygnus is good ATM. HTH

Hi Leave the diaphragm open and control the f ratio using a 58mm to 36mm step-down ring(s). That will help control the diffraction spikes and the irregular colour.

Yes. Remove the paper insert and apply a generous blob of silicone to coincide with the original cork. Allow the mirror to seat under gravity (don't push it home) on a level surface until a representative blob under the same ambience returns to shape upon being distorted. Then refit. Neutral, pH 7ish, without carboxylic acid is best. Any translucent sealant will however do better than none, but note silicone, not acrylic. The silicone limits the lateral movement of the mirror hence helps retain collimation regardless of tube angle, but don't forget to upgrade the mirror springs too, that the floating part of the mirror support affords the same limitation without locking screw distortion. HTH

Hi 600d, so it's essential to lose the dark frames. Do not use bias frames taken via the camera, instead simply subtract a constant value of 2048 as the bias value using the software as @ONIKKINENsuggsets, above. The horizontal bands are in the red and are easily removed: T The diagonal bands are in the blue and green and almost certainly due to haze or cloud. Simply stack without those frames using e.g. sigma 3-3. HTH

Hi everyone Not exactly the brightest of targets, but we have our sharp Newtonian back for the weekend so just time for a few stragglers before it points permanently toward Sagittarius for the rest of the season. One taken without filter and the other with a UHC extracted HOO. Not sure which works best; a bit more detail beginning to show in the latter perhaps. Thanks for looking. Any dslr user tips on this one most welcome. 700d on gso203, ISO800

Hi and thanks for posting. Had to reference it. It is indeed double. kstars has it as hd136202 with LH3060, an orbiting double. Never noticed it before. You can probably see why. Here's the same target before removing the primary mirror clips:

The 200pds mercifully does not have a cardboard insert. Instead, it has cork pads placed to coincide with the circumference of the mirror; unfortunately, far from the optimal support points:( Wherever you see cork, put a blob of silicone to extend over the cork with sufficient to spread to either side of the cork and up the side of the cell. Do not push the mirror into the cell; leave it to settle under gravity on a level surface. Keep a blob of silicone separately but under the same conditions to guage when it has polymerised to the extent that it returns to its original shape when deformed. Then refit to the tube. HTH

This company. The same length and diameter as your existing springs, but in 1.6mm wire. Place your order dimensions at the checkout. HTH

Hi Flex is very common on low end reflectors. To be able to analyse the guiding and star shapes, we'd recommend getting the mechanical integrity of the telescope as good as possible. We've not yet witnessed an out of the box pds which holds collimation. To guide a 1000mm focus reflector, a modified finder telescope in the supplied shoe will almost certainly be introducing avoidable error. For collimation to hold at all tube angles (not just the one at which you performed the collimation) the tube needs stiffening: spread the tube rings on a 50cm Losmandy dovetail. The top of the rings then need joining with a rigid metal profile and the guide telescope bolted directly to it. The SW primary mirror springs need replacing with six 1.6mm wire versions: three replacements and the other three as passive versions over the locking screws. Leave the latter loose. To prevent lateral movement of the primary, it needs to sit in the cell on neutral silicone sealant to coincide with the SW cork. Lose the mirror clips in the process. Even better, both the modifications and an oag. You may even get away with just the latter. Cheers and HTH

Stress as we may, at the end of the day, we're never going to turn a €200 SkyWatcher into anything like a mechanically and optically sound top of the range reflector. We can have fun trying of course, but far better just to go out with whatever stuff you have and... Use it:) Anyway, long hot moonless night ahead. Let's make the most of it. Cheers

The focal length remains exactly the same. This is not the reason the f ratio changes. You are instead reducing the effective diameter of the primary as now, not all of it will be intercepted by the secondary: 130mm is reduced to (guess) 110mm.

Yes. A 10mm m48 ring.

Given that you'll no longer be using the full diameter of the primary mirror, yes. Bear in mind however that a 130mm mirror with a fl of 650mm will always be f5. The main disadvantage is that if you move the primary mirror 20mm up the tube, the standard issue secondary will not intercept all the light the primary offers. Visually imperceptible. Imaging wise, losing valuable light; imagers need every microgram of light they can possibly muster;)