Time for resilvering?

[markse68]

Last night I took my trusty Tal-1 to a new viewing site- the common right near my home in Plumstead with a much better view of the horizon and a bit further away from direct street lighting- and what a difference it made! Saturn which up till now had been the boring cousin of magnificent Jupiter suddenly revealed its beauty- Cassini division, shadow of rings and even hints of banding! Up till now it had been just a homogenous blob with ears 😉 BUT Jupiter really disappointed. I tried a few eyepieces but I was getting terrible flare in a broad hazy cross centred on its disk. It wasn’t enjoyable to view at all. I worried my scope had gone out of collimation but then why Saturn so clear? I think I may have reached the limits of my primary in its original poor condition. Could this (bacterial/mould?) damage be causing the flare I’m seeing and is it time for resilvering?

[Ricochet]

The pattern of the marks does indicate fungal growth so I think you would at least want to look into cleaning the mirror with something that will stop that. I'm sure someone will know what works best. As for recoating, that may or may not be necessary. It takes quite a bit of damage on a primary before it noticeably affects the view, you will most likely notice it if the damaged areas are shiny like scratches would be. 

With regards to the bright cross, that would be the diffraction spikes due to the secondary spider, just like you get with bright stars but wider as the planet is wider. I would guess that you usually observe at higher magnifications where the spikes are less visible but conditions have meant you have used lower, brighter magnifications. 

[markse68]

Thanks Ricochet. It wasn’t as much a bright cross like the diffraction spikes from bright stars but more like a hazy smear but yes maybe that’s what it was. Tbh I was on the way home and pretty tired and it was late so I didn’t hang around long- the scope surely hadn’t temp equalised. But it was worth it for Saturn 😊