Newbie question :)

[hornedreaper33]

Hello all. I joined the forum a little while ago but this is my first post because... today was telescope day!! I've wanted one for ages and finally took the plunge while I'm earning some decent wonga with a Celestron Advanced VX 8 SCT.

So what I have learnt from trawling the posts is that dew control is a must with the SCT and I think I'm going to attempt a camping mat based dew shield so I can make it a little longer than the commercially available ones.

I've not had much chance to play because as luck would have it, it's completely overcast. However, should I expect the aluminium dovetail to get easily damaged by the clamp? I am certain I haven't over tightened it but the anodising is already showing signs of use.

Secondly, I am assuming that the RA and DEC clutches must be engaged when you power up the mount?

Which leads me to my final question, when the clutches are disengaged are you free to move the mount as much as you like or should you be careful not to move it around to quickly?

Thank you. Fingers crossed for some clear sk skies.

[Langy]

Welcome to the SGL, I'm sure someone will soon be here with all your answers as I know nothing about your scope.

I would suspect that if you release the clutches that you can move the scope around at your leisure.

[YKSE]

First of all, a warm welcome to SGL.

A dew shield can only delay dewing, a dew heater is needed when it's really humid, but you'll find it out later.

The dovetail will easily show sign of use, nothing to worry about.

You're right about the clutches, have them engaged when using the motor to move the scope, and disengage them when you want to move the scope by you own

There's no need to move the scope quickly, we can't use the scope to follow a meteor.

[jonathan]

In fact, a couple of good screw marks in your dovetail plate will be a handy guide for quick balancing of the scope the next time you come to attach it to the mount.

That Celestron Advanced VX mount looks nice, wish it was around when I was looking at buying the 8SE.

[ronin]

You can release the clutches to move the scope, however if the system is a goto then do not.

If the goto is aimed at M42 and you release the clutches and go to M45, then as far as the scope is concerned it is still pointed at M42. So the next goto movement will be as if it was pointed at M42 whereas it is pointed elsewhere.

I don't know the mount and what it is or does.

[brantuk]

Hi and welcome to SGL

Sct's really are dew magnets - the corrector plate gets misted up very easily when there's the least bit of dew in the air. You'll need a dew band and controller as well as a dew shield for effective use. I power my dew control separately to the scope power (ie another battery or ehu on campsites).

The dovetail will become marked - it's an inevitable thing with all scopes. You can get fancy mounting plates like ADM which are very firm and don't use a bolt directly onto the bar - it's more of a clamp/vice arrangement - but you made need to change the mount shoe to accommodate them.

The RA and Dec axes must remain locked after you've aligned the mount properly - otherwise you'll loose the alignment and have to restart from scratch. So it's really an "either/or" decision when you choose to use the mount manually or electronically. But it's nice having a "manual" backup if the battery goes flat - at least you can continue the session without electronics. But slew around carefully when the clutches are unlocked, holding onto the scope at all times, so it doesn't take a dive at the tripod legs.

[hornedreaper33]

Thank you for the warm welcome and helpful replies. No doubt I'll be back with more questions when I finally get to use it. I might try to aim between the clouds tonight.

[Owmuchonomy]

My Celestron 9.25 is a massive dew magnet just like the member said above.  Small investment required to solve the problem.  £35 for a Kendrick dew heater and about £2 spent in Maplin to make up a lead.  Greenwitch sell them.

[jonathan]

I use the HitecAstro four-channel dew heater controller with my 8SE, I find it very good and like that I only need one power lead to the battery as I can plug the mount and dew heater tapes directly into the dew heater controller.  It's not just the corrector plate (the big glass plate covering the end of the scope) that can dew up, you will have nights when the finder will dew up and the eyepiece too, so having a few heater tapes is no bad thing, but each one draws power so consider power requirements.

As far as choice between manual or electronic goes, you can still use the hand controller to slew the scope without the goto function or alignment, it will act just like a SynTrek (non-goto) and so should still track providing that you at least align the mount correctly - point its N leg North, or at Polaris, and you can't go far wrong.  The manual should hopefully say something about this.  When not using the goto feel free to release the clutches to quickly point the scope at something, then engage the clutches and use the finder scope and motor drive to home in (alter speed for fine adjustments), use a 25mm eyepiece to start with and increase the magnification once you have the target centered.

[hornedreaper33]

My Celestron 9.25 is a massive dew magnet just like the member said above.  Small investment required to solve the problem.  £35 for a Kendrick dew heater and about £2 spent in Maplin to make up a lead.  Greenwitch sell them.

Don't you need the controller to run the heater?

[Owmuchonomy]

Don't you need the controller to run the heater?

Depends on the reliability of your power supply.  I use a well regulated observatory type power supply (one of my primary investments at about £60).  The band for my 9.25 corrector plate pulls about 1.2 amps.  I therefore don't use a controller as it would be a waste of money and they aren't cheap!  I did make up a fused cable though as I said using parts from Maplin.  I never have trouble with eyepieces and finders dewing up but other members do so you may need a multi port controller if you have more than one band.

[clarkent]

Pity that most of the accessibly-priced EQ mounts do not have dual encoders so you can slew manually and keep goto functionality.  

Yet a good Dobo goto mount does have them but is poor for astrophoto tracking.  

Does anyone know if dual encoders can be added to EQ mounts from some specialist supplier?

[jonathan]

The only caveat with an uncontrolled dew heater tape would be overheating the scope, if the tape puts too much heat into the metal it may result in disturbed air travelling out of the end of the tube as the heat escapes.  In reality if the tape is designed not to generate much heat (should be just enough to keep the tube above the dew point) then this wouldn't be a problem, my tapes do not get hot, only mildly warm, even when turned up to maximum on my controller, but I use the controller so that I can attach up to four tapes (I have three) and also I can plug my mount into it which makes the wiring easier to manage to the battery.  Mine is a portable setup, no permanent observatory for me.