alacant

Hi None of the low end rolled steel tubes we've witnessed hold the mirror cell and focuser fixed relative to each other sufficiently well so as to hold collimation as the tube changes angle, especially with a camera attached. There are some simple modifications which are needed on such telescopes to make them into reliable astrographs, These include fitting stronger primary mirror springs, sealing the mirror to its cell, and replacing the secondary support with a light plastic version. However, before replacing the focuser [1], I believe in the case of the vx, the most urgent change you'll need is to spread the tube rings at least 50cm apart on a Losmandy dovetail plate. Then tie the top of the same using rigid aluminium profile. We use 2mm wall 2 x 6 cm aluminium box section for this. This should make the tube rigid enough to obviate the need for the CF upgrade and so eliminate tube flexure from your debugging. Install the other modifications until the collimation holds at all angles. Visualisation here. Cheers and HTH [1] IIRC the focuser on the vx example we used was fine after adjustment of the tension, but note we only tried it with a dslr. If you're monochrome, you're probably going to have to reinforce the tube around the focuser circumference as well as the other modifications we outlined.

We didn't think so either until we tried with and without. No obligation of course, but making an astrograph from a bottom of the range Newtonian, you need every bit of help you can get. Of course, the locking screws are left in place merely to retain the extra springs; loose. @laser_jock99 is the pioneer of the technique. All credit to him. Cheers

Hi We've yet to find a low end reflector -the ones with with three weak springs- hold collimation at varying tube angles. Cheers and HTH

For 200mm mirrors, we use 1.6mm. This covers all 200mm SW possibilities, including the older thick Pyrex glass type. You'll find that if the mirror is held to prevent lateral motion by silicone, you'll rarely need to touch the adjusters. Cheers

For future reference (at sensible prices), simply specify your dimensions at the checkout in the message box here: https://a.aliexpress.com/_uI3HoG The dimensions to give are as below. Ask for Europe shipping. HTH

Well done. You're on your way to a Newtonian which holds collimation at all tube angles, not just the one at which you collimated. One less thing to have to compensate for:)

If you're staying with it (it can be done, but the telescope has to be mechanically perfect), the guide telescope needs mounting directly to a rigid rail joining the top of the tube rings. We use 2mm wall 60 x 20 box section aluminium. The rings themselves need mounting further apart on a Losmandy dovetail. For a 203 f4, go for 45cm separation. This provides adequate support for the flimsy gso tube. If flex remains, the next step is a lightweight secondary support. Or just go for an OAG. HTH

No, no. The washers go on the outer part of the cell such that when the spring is fully compressed, the screw has not travelled far enough to foul the glass. To save on washers, we use nuts with a washer either side:

The focuser doesn't mount to the tube, rather its base. The latter -mercifully- mounts metal-to-metal to the tube.

Also forgot. Again... Don't forget to replace the springs. As a minimum, 1.4mm wire. 3 replacements and a further three using the white-knob screws as retainers. Cheers

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